ESP32-D0WD-V3 revision v3.0 v revision v3.1 problems

[Acuario]

Hi,
I have a custom board design that uses the ESP32-WROOM-32E module.
I am encountering strange problems between the v3.0 and v3.1 versions of the ESP32.
I am using GPIO12 and GPIO13 as a secondary I2C bus. I have 10K pullup resistors to 3.3V and the I2C bus is connected to 2 x ADS1115 ADC chips running at 5V. At idle GPIO12 is approximately 2.49V

I have 4 identical boards, 2 with v3.0 and 2 with v3.1
Both v3.0 boards work perfectly. Both v3.1 boards have the same problem so it seems to be related to the chip revision. Something has changed in the silicon that causes this problem between v3.0 and v3.1 but I cannot find any documentation of the change.

With v3.1 I have problems.
Chip type: ESP32-D0WD-V3 (revision v3.1)
I cannot do an upload of my code using the serial port unless I tie GPIO12 low before performing a reset. If I try without holding it low on reset and during the upload then I get an MD5 checksum error at the end of the upload.
After my code has loaded and is running I cannot create or modify any parameter in the nv memory. I can read values stored there but writes of any type do not work. I get a successful message back from the preferences library but my value is not stored.

On the boards with the problem I have moved the I2C onto GPIO14 and it works perfectly.

There appears to be a bug with the v3.1 devices and GPIO12 that prevents any modification of the flash contents other than in the boot download mode.