Hey Janosch, I’ve been down the sync rabbit hole myself. From what I’ve gathered, the EOS M3 might not be great for precision sync due to the DIGIC 6 processor limitations. I’ve played around with CHDK, and it usually can’t handle hardware tweaks like changing the period counter max on those cameras. I’d suggest checking out cameras with better sync options or using timecode generators for a more reliable setup. It’s a bit of a hassle, but it might save you headaches down the line.