I found intermittent instability problems when writing to MPU6050 registers, though reading registers is always OK.
I read the schematic and found the device uses 2k2 pullup resistors. Since Rpi I2C pull up is 1k5. So with 2k2 might be too strong, especially I am using long connecting wires.
So I decided to remove the MPU6050’s built in resistors, as shown below.
After the operation, everything seems OK, but of course I need wait longer and see.