PreArm Mount: check TYPE on Speedybee F405 v3

Hi,
I’m trying to set Siyi A8 mini UART control on Speedybee F405 v3 with AP 4.3.7. I have done full config described here: SIYI ZR10, ZR30 and A8 Gimbals — Copter documentation
When I change MNT1_TYPE to 8, I get PreArmMount: check TYPE. I got rid of error when I set type to 5, but camera control does not work. Only video and power supply work correctly.
All GND wires are connected (every plug has one of them). I also tried to swap wires between RX and TX. I’m sure that SERIAL3 is my RX3 and TX3.