Shortcuts bar does not unhide in Firefox

**Describe the bug**
With shortcuts set to "tab/menu bar" the bar is autohidden (upwards) after a number of scrolls, or if a post is opened. It doesn't then reappear when the post is closed, or if the timeline is scrolled back up. The only way to get it to reappear is to refresh the page, or use the menu options to go to another page (e.g. "local" or "notifications"). This happens in Firefox 122.0.1 and FF 123.0 as well as the FF fork Floorp 11.10.2, based on FF ESR 115.8.0. I can't reproduce it in a Chromium browser.

- Which site: phanpy.social 2024.02.03.35a31e1
- Which instance: mastodon.ie

**To Reproduce**
Steps to reproduce the behavior:
1. Switch shortcuts to display as "tab/menu bar".
2. Add shorcuts for "home", "notifications", "local", and two or more multi hashtag search terms.
3. Scroll down a few posts, or open any post which isn't the top one of the home feed.
4. See error

**Expected behavior**
Tab/menu bar either auto-unhides at scroll up (as the menu button does) or closing of the post.

**Desktop (please complete the following information):**
- OS: Windows 10 Enterprise and Windows 11 home
- Browser: Firefox and Floorp
- Version: 122.0.1 and 123.0 + Floorp 11.10.2, based on FF ESR 115.8.0

**Additional context**
This isn't new. I've noticed it for some time but only got around to filing this now. May be related to #300?