Screen and touch freezes randomly

Hello, I created a thermostat using lvgl 8.0 for the gui and it works quite well, except sometimes the screen completly freezes: it doesn’t react to touch and even the measured temperature is not updated on the screen.
It doesn’t happen as reaction to specific gesture: it just happens after some time it works normally, even without any interaction with the user.
The main program doesn’t crash, in fact I have a running watchdog (WDT), but the device is not rebooted.
I have enabled lvgl log with WARN level and a callback to write to file, but nothing is logged (I cannot raise the log level, or too much info is written - I only have 2MB and most of it is already taken by the firmware).
I am using rpi pico with ili9xxx driver for the screen and ft6x36 driver for the touch.
I would appreciate if anyone can give some hint to solve the problem or at least debug it.