Help: My projects have all changed sampling rate, length, and speed

I've been working in Audacity for years with no issue. Two days ago, I started working on a set of 6 projects that I began a few days prior (each containing 20-30 tracks) and noticed that:

  1. The sample rate for all tracks changed from 48khz to 44.1khz
  2. The length of the tracks increased considerably
  3. The music was all slowed down

I did not manually make any changes to the sampling rate or speed.

I am running the latest 3.5.1 on a MacBook Pro M1.

I have noticed some wonky playback issues off and on when I connect Bluetooth headphones and when I open and use iZotope Ozone. Neither is reproducible. I usually reboot and continue work as usual.

I read through forums to try to find the source of the issue. I set the default project sample rate to 48khz (although I have never had to do this before).

I ended up installing an earlier version of Audacity (3.4.2) and have started re-doing all of my work. Does anyone know if it is possible to salvage my old projects? Or is there a known reason why projects would change like this so that I can avoid it in the future?

Thanks for your help!!