I2C error when GOPlus servo + Grove Ultrasonic sensor

[Serge]

Hi
i try to use servo connected to GOPlus module and UtraSonic sensor SR 04.

The SR04 with the classical 4 pins (trig and echo) works well alone (pin 21 and 22 )
When a servo is connected : it doesn't work anymore : i2Cbus error 110 (detail : File I2c-bus.py line 41 in write_U8 OSError 110.

I thought first it was a problem with SR04 connexion on pin 21 and 22.
So i wanted to try the grove US sensor. But i didn't find a unit block.
(see https://forum.m5stack.com/topic/1907/uiflow-and-unit-grove-ultrasonic-distance-sensor)

But i ve found this morning :
The I2C Error 110 occurs when Grove US sensor is connected on Port A and the servo stopped.
There is no similar error when Grove US sensor is connecter to port PB1 on GOPLUS module

Why ?