I2C issue with GM12864-59N LCD

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I's using an I2C LCD of Type GM12864-59N together with a RP2040-Zero.
The constructor is:

U8G2_ST7567_ENH_DG128064I_1_2ND_HW_I2C u8g2(U8G2_R2,U8X8_PIN_NONE)

The display is working "mostly" well, as long as long as it is used on the breadboard.
There are some watchdog resets from time to time, but I was thinking this was cased by the breadboard.

After creating the PCB the display is working only sometimes and only some displays with some RP2040-Zeros.

I removed the diodes from the board, as my circuit is using 3.3V and also tried different pullups (after removing the original ones) and also removed the inline resistors from the LCD Board.

I checked the I2C communication with the oscilloscope and the ACKs from the display look strange.

The Voltage doesn't drop to ground. Instead it is mostly just around the low threshold of the RP2040 (0.8V).
This is worse on the PCB than on the breadboard.
So i assume that sometimes the ACK is not recognized as ACK.

According to this page: https://ahmadsarraj.com/learning-lab-advanced/troubleshooting-i2c-issues/
This could be "Unintended Contention".

I've run out of ideas and would appreciate any suggestions for solving this problem.