diff --git a/app/client/components/ViewLayout.ts b/app/client/components/ViewLayout.ts
index 12efaa90..f017f992 100644
--- a/app/client/components/ViewLayout.ts
+++ b/app/client/components/ViewLayout.ts
@@ -334,7 +334,12 @@ export class ViewLayout extends DisposableWithEvents implements IDomComponent {
 
     function addToSpec(leafId: number) {
       const newBox = tmpLayout.buildLayoutBox({ leaf: leafId });
-      const rows = tmpLayout.rootBox()!.childBoxes.peek();
+      const root = tmpLayout.rootBox();
+      if (!root || root.isDisposed()) {
+        tmpLayout.setRoot(newBox);
+        return newBox;
+      }
+      const rows = root.childBoxes.peek();
       const lastRow = rows[rows.length - 1];
       if (rows.length >= 1 && lastRow.isLeaf()) {
         // Add a new child to the last row.
diff --git a/app/client/components/duplicatePage.ts b/app/client/components/duplicatePage.ts
index a4e01775..c8e996f4 100644
--- a/app/client/components/duplicatePage.ts
+++ b/app/client/components/duplicatePage.ts
@@ -199,13 +199,20 @@ function newViewSectionAction(widget: IPageWidget, viewId: number) {
 /**
  * Replaces each `leaf` id in layoutSpec by its corresponding id in mapIds. Leave unchanged if id is
  * missing from mapIds.
+ * LayoutSpec is a tree structure with leaves (that have `leaf` property) or containers of leaves. The root
+ * container (or leaf) also includes a list of collapsed leaves in `collapsed` property.
+ *
+ * Example use:
+ *   patchLayoutSpec({
+ *     leaf: 1,
+*      collapsed: [{leaf: 2}]
+ *   }, {1: 10, 2: 20})
  */
 export function patchLayoutSpec(layoutSpec: any, mapIds: {[id: number]: number}) {
-  return cloneDeepWith(layoutSpec, (val) => {
-    if (typeof val === 'object' && val !== null) {
-      if (mapIds[val.leaf]) {
-        return {...val, leaf: mapIds[val.leaf]};
-      }
+  const cloned = cloneDeepWith(layoutSpec, (val, key) => {
+    if (key === 'leaf' && mapIds[val]) {
+      return mapIds[val];
     }
   });
+  return cloned;
 }
diff --git a/test/nbrowser/ViewLayoutCollapse.ts b/test/nbrowser/ViewLayoutCollapse.ts
index b1643e66..d157bc6b 100644
--- a/test/nbrowser/ViewLayoutCollapse.ts
+++ b/test/nbrowser/ViewLayoutCollapse.ts
@@ -16,11 +16,86 @@ describe("ViewLayoutCollapse", function() {
 
   before(async () => {
     session = await gu.session().login();
-    await session.tempDoc(cleanup, 'Investment Research.grist');
-    await gu.openPage("Overview");
+    await session.tempNewDoc(cleanup);
+  });
+
+  it('fix:copies collapsed sections properly', async function() {
+    // When one of 2 widget was collapsed, the resulting widget can become a root section. Then,
+    // when a page was duplicated, the layout was duplicated incorrectly (with wrong collapsed
+    // section). This resulted in a bug, when the root section was deleted, as it was the last
+    // section in the saved layout, but not the last section on the visible layout.
+
+    // Add new page with new table.
+    await gu.addNewPage('Table', 'New Table', {
+      tableName: 'Broken'
+    });
+
+    await gu.renameActiveSection('Collapsed');
+
+    // Add section here (with the same table).
+    await gu.addNewSection('Table', 'Broken');
+
+    // Rename it so that it is easier to find.
+    await gu.renameActiveSection('NotCollapsed');
+
+    // Now store the layout, by amending it (so move the collapsed widget below).
+    const {height} = await gu.getSection('NotCollapsed').getRect();
+    await dragMain('Collapsed');
+    await move(gu.getSection('NotCollapsed'), { x: 50, y: height / 2 });
+    await driver.sleep(300);
+    await move(gu.getSection('NotCollapsed'), { x: 100, y: height / 2 });
+    await driver.sleep(300);
+    await driver.withActions(actions => actions.release());
+    // Wait for the debounced save.
+    await driver.sleep(1500);
+    await gu.waitForServer();
+
+    // Now collapse it.
+    await collapseByMenu('Collapsed');
+
+    // Now duplicate the page.
+    await gu.duplicatePage('Broken', 'Broken2');
+
+    // Now on this page we saw two uncollapsed sections (make sure this is not the case).
+    assert.deepEqual(await gu.getSectionTitles(), ['NotCollapsed']);
+  });
+
+  it('fix:can delete root section', async function() {
+    // But even if the layout spec was corrupted, we still should be able to delete the root section
+    // when replacing it with new one.
+
+    // Break the spec.
+    const specJson: string = await driver.executeScript(
+      'return gristDocPageModel.gristDoc.get().docModel.views.rowModels[3].layoutSpec()'
+    );
+
+    // To break the spec, we will replace id of the collapsed section, then viewLayout will try to fix it,
+    // by rendering the missing section without patching the layout spec (which is good, because this could
+    // happen on readonly doc or a snapshot).
+    const spec = JSON.parse(specJson);
+    spec.collapsed[0].leaf = -10;
+
+    await driver.executeScript(
+      `gristDocPageModel.gristDoc.get().docModel.views.rowModels[3].layoutSpec.setAndSave('${JSON.stringify(spec)}')`
+    );
+
+    await gu.waitForServer();
+
+    // We now should see two sections.
+    assert.deepEqual(await gu.getSectionTitles(), ['NotCollapsed', 'Collapsed']);
+
+    // And we should be able to delete the top one (NotCollapsed).
+    await gu.openSectionMenu('viewLayout', 'NotCollapsed');
+    await driver.findContent('.test-cmd-name', 'Delete widget').click();
+    await gu.waitForServer();
+
+    await gu.checkForErrors();
   });
 
   it('fix: custom widget should restart when added back after collapsing', async function() {
+    await session.tempDoc(cleanup, 'Investment Research.grist');
+    await gu.openPage("Overview");
+
     const revert = await gu.begin();
 
     // Add custom section.
diff --git a/test/nbrowser/gristUtils.ts b/test/nbrowser/gristUtils.ts
index 96fce930..b53faa3a 100644
--- a/test/nbrowser/gristUtils.ts
+++ b/test/nbrowser/gristUtils.ts
@@ -1186,6 +1186,27 @@ export async function addNewPage(
   await driver.wait(async () => (await driver.getCurrentUrl()) !== url, 2000);
 }
 
+export async function duplicatePage(name: string|RegExp, newName?: string) {
+  await openPageMenu(name);
+  await driver.find('.test-docpage-duplicate').click();
+
+  if (newName) {
+    // Input will select text on focus, which can alter the text we enter,
+    // so make sure we type correct value.
+    await waitToPass(async () => {
+      const input = driver.find('.test-modal-dialog input');
+      await input.click();
+      await selectAll();
+      await driver.sendKeys(newName);
+      assert.equal(await input.value(), newName);
+    });
+  }
+
+  await driver.find('.test-modal-confirm').click();
+  await driver.findContentWait('.test-docpage-label', newName ?? /copy/, 6000);
+  await waitForServer();
+}
+
 export async function openAddWidgetToPage() {
   await driver.findWait('.test-dp-add-new', 2000).doClick();
   await driver.findWait('.test-dp-add-widget-to-page', 2000).doClick();