Hi! I was wondering if you found a solution to this? I'm having the exact same issue with the exact same camera (G7x Mii) and strobe (YS-D2).
In TTL mode the strobe fires out of sync. In manual mode (orange) it fires correctly. I tried the strobe on a different camera in TTL (canon S110) and it works fine.
As for settings, Im testing at ISO 125, F5.6, 1/125 shutter. Strobe in TTL mode (light blue) with EV comp set at 0. Any help would be greatly appreciated. I spoke to the camera shop and they couldn't figure it out either and want me to send it in. Trying too avoid it because I live in Cabo San Lucas so will be a mission to get it back to the US and then back to me.
Thanks in advance!