Expanding the sidebar to make it bigger is not affected, only when trying to make the sidebar smaller again.
Steps to reproduce:
1. Make an HTML export containing many pages
2. Open the HTML export in a browser
3. Pull out the navigation bar far to the right
4. Try to pull it back again
Expected result: The navigation sidebar can be resized smaller
Actual result: The navigation sidebar stays frozen in its position
Workaround: When the mouse cursor changes to the expandable resizing icon cursor for the sidebar, make sure to keep it close to the borderline for the sidebar. Then, move it slowly when resizing the sidebar to a smaller state so that cursor always stays close to the sidebar border.
As soon as the resizing action is made quickly and the cursor moves away from the sidebar border (ie. goes closer to the page title content in the sidebar), the smaller resizing will stop and cause the issue.