Display printing lines and rubbish after a while

What do you want to achieve?

Understand why my display is going crazy.
I am working with a Lilygo T-Watch 2021 and I have loaded an arduino sketch with a UI made with SLS. Everything has been working fine for several days but in the last couple of days my screen started showing patches of horizontal lines, or showing the frame of a label (supposed to be invisible) or not showing anything at all (just backlight).
Program is working fine, as shown by the serial monitor and other interfaces. The issue is just with the display.

What have you tried so far?

  1. I suspected a HW problem and repeatedly plugged and unplugged the display. Didn’t solve it.
  2. I suspected a problem with memory (I uploaded different versions of the code dozens of times). So I erased the flash memory of the chip with the esptool procedure ( ESP32: Erase Flash Memory (Factory Reset) | Random Nerd Tutorials) Didn’t solve it.
  3. I loaded the code on a new identical board+display set and THAT appears to solve the problem!!! But I can’t think of a hardware problem because I have already plugging and unplugging the display and the problem persists…

Any suggestions?
Thanks in advance