Flash only going off on 2nd shot

[hedonist222]

Hello everyone

Sony a7rv
Backscatter mf-1
S-TURTLE TTL trigger

Flash on camera set to fill-in mode

The flash doesn't go off on first shot
It only goes off if I do two quick consecutive shots and only on the second shot

Ideas?
Thank you

 

[Barmaglot]

You're probably running into this issue: Oh, Backscatter - Why do your MiniFlash strobes taunt me so?