Steps to reproduce the behavior

Prereq. Possibly need a site with hundreds if not thousands of pages, like FG.

1. Go to My Sites > Pages.
2. Open a page.
3. Open the right sidebar.
4. Expand the Page Attributes section.
5. Begin typing in a page name. In the FG, try searching 'Quality engineering'.

What I expected to happen

Pages matching the search query are shown in a dropdown list.
The dropdown list remains static as long as the search query is not modified.

What actually happened

Not all pages matching the search query are shown in the dropdown.
The dropdown may briefly display entries that match the query in Step 5, but the entry quickly disappears.

This issue may be intermittent.

Context

Editing the FG.

Browser / OS version

OS: macOS Big Sur 11.1 (20C69)
Browser: Firefox Nightly 87.0a1

Is this specific to the applied theme? Which one?

Uncertain - it was reproduced on FG.

Does this happen on simple or atomic sites or both?

Tested on Simple.

Is there any console output or error text?

No.

Level of impact (Does it block purchases? Does it affect more than just one site?)

Moderate.

Screenshot / Video: If applicable, add screenshots to help explain your problem.