So this one is new (to me):
I have a PCA9555DB port extender, and it works just like I want it, but only if I add the Wire.begin() in my setup (logical).
I have a PCF85134HL LCD display controller, and it DOES work but only if I remove the Wire.begin() from my code! It runs normally with all the wire functions (Weird stuff!).
Unfortunately, I have both in my project so I need to fix this somehow, but it's above my skills ATM. I could post my code, but not sure if the fault is in there, both IC's work, just not together.
I tried disabling the internal pull-ups, didn't work. Anyone have an idea where to look?