Snap, Crackle, and pops on play and stop

[Thenewexhibit]

I seem to be getting strange snap, crackle, and pop noises when starting and stopping sessions.

It doesn't seem AS loud when I have a dense session of tracks running, but I'm mixing a piano track with nature sounds, and every start and stop has a snap, crackle, or pop sound. Kinda annoying now that I hear it. Does anyone know what this is?

I'm on PT 2021.12.0 on a Mac Trashcan with 10.15.7, 32GB ram, 1TB internal SSD, sessions running off of 2TB external Sandisk Extreme Pro SSD with a Saffire Pro 40 connected via firewire to thunderbolt adapter. Once again, never really noticed this until working on an intimate piano track where you're brightening things up.

[Darryl Ramm]

Important things are likely to be...

Are the noises recorded in the signal in Pro Tools (you can see them in the waveform?) or added on playback?
If you open the session and let the disk cache fill (go green) and then press play does this happen less?
IO buffer size?... does this go away at large sizes?
What sample rate? If very high try it at 44.1kHz.
Run with ignore errors not checked - does Pro Tools crash?
Do you have any digital I/O into the interface? How is that clocked?
Removed cellphones etc from the immediate error?
Share the sound somewhere online... if it's really strange folks may have an idea what it is.