@Zing

This was all on a fresh clean install...

It seems I somehow sorted it out:
Went hunting for BIOS roms and installed all the one I found (even and especially the optional ones).
Additionally I also slightly overclocked the pi zero (though I don’t believe it had direct effect on the freeze issue; makes it overall run better though).

So far I don’t experience the same issue anymore so I believe it was due to the fact the pi zero is a bit limited in computation power so it really need BIOS installed (even optional ones). or so it seems...

Thanks for the feedback though! Very much appreciated!

Recalbox version:7.1.1 (downloaded from recalbox website, flashed with etcher)
Platform: raspberry pi zero w
Disk: sandisk class 10 sd card
Controller: stock sony ps3 dualshock
Screen: computer screen plugged via hdmi

Seem to experience some issues for which I found no explanation so far:
My system systematically freezes/crashes when getting back to menu from any emulator using hotkey+start on the controller.
The pi seems to be calculating/working hard but stays on black screen forever, forcing me to hard shutdown.

Menu, screen, audio, ps3 controller and wifi all work fine (though wifi in menu seems a bit buggy).
Some emulators do load and work find but the exit/crash seems systematic.

Also noted the following issue (maybe not related):
Added a valid atari lynx bios and loaded roms but the emulators (both libretro handy and mednafen lynx) seem to load up to game splash screen then the pi freezes (on lots of games).

Is there a ay to fix this?
It’s a bit annoying to have to hard shutdown every time...