So quick update based on recent observations:
I've read a lot about it and it appears it is especially observable for Creality products.
Tried few suggestion such as manually setup the USB device on Octoprint, or force the Baudrate to 11500-ish, without any success.
I stopped printing using Octoprint for any project above 2 hours as they kept crashing with the same error.
Lastly I've tried to read SD card from Octoprint and launching the printer remotely to still have access to Timelapse (not Octolapse unfortunately). The output is that even by launching the print straight from the SD, the printer started to fail again.
So my theory (as a noob) is that the connection between the PI and the printer is where the problem occurs. Not the electrical supply (because of UPS), neither the printer local setup (as prints are fine when disconnected from Octopi).
I'll order a new PI and a new USB.A > USB Mini cable today, and see if the issue persist.