I just tried the X1-S on my Sony A7
With V860 for Canon & X1 receiver :
-M mode works ok
-TTL mode works but adding and substracting flash exp compensation has no effects
-HSS works ok and automatically above sync speed up to 1/8000, no banding
With V860 for Canon and XTR16s :
-M mode works ok
-HSS works ok like above (you have to turn on HSS mode on the flash)
With AD360 II for Canon :
-M mode works ok
-TTL mode works but adding and substracting flash exp compensation has no effects
-HSS works ok and automatically above sync speed up to 1/8000, no banding
With TT685 for Sony
-M mode and TTL mode works ok including flash exposure compensation
Since I dont need TTL mode, I end up buying X1s for my A7, XTR16 for my old AD360 and XTR16s for my V860 Canon

My AD360 II needs no additional receiver.
The FEC not working is a significant incompatibility. Did you try the camera FEC to see if its passed along.
Sony with Sony the camera FEC is additive.


