Navigation bar glitching up and down on Firefox for mobile

[foxeddev]

Please confirm the following.

• I checked the existing issues for duplicate problems
• I have tried resolving the issue using the support portal

What browsers are you seeing the problem on?

Firefox

Describe the bug

The navigation bar on mobile is too far up (hiding some menu options) and glitches up and down when scrolling.

Screen recording

Steps to reproduce

Open any Modrinth page on a mobile device with Firefox.

Expected behavior

The navigation bar should stay fixed at the bottom of the screen.

Additional context

Possibly related to #3171?

[huhuhuhuheh]

4seEU9l.mp4

For those who don't want to visit imgur, here's the video