ard_newbie:
See this thread:Electromania: Clock and calendar using Arduino due internal RTC and I2C LCD display
Maybe SDA and SCL lines receive EMI spikes, and these spikes are considered as valid signals by I2C master.
Several workarounds exist to suppress spikes, one of them in this thread, reply #8:
Arduino Due HMC5883l - #9 by MartinL - Arduino Due - Arduino Forum
Thanks. I've tried resistors as mentioned in reply #8. Sadly my LCD still freezes.
Probably it will be just easier/faster to solder all the connectors well to the LCD and forget about i2c controller...