ESP32 UART receive error after a pause in communications

[Ivan32]

UART receives incorrect first two bytes if there was no RX communication for a few seconds. If communication goes continuously, no errors occurs.

The chip hardware version 3.0 ESP32-Pico development board works OK. I can see it only with 3.1 ESP32-U4WDH chip. In both ESP IDF versions, v5.1 and v5.4.0 it is the same.

Turning auto baud rate detection On or Off does not affect this. Changing communication speed also does not affect. I am using UART0 for tracing and UART1 for actual communications with ESP32.

On a single PCB I have 2 MCUs and one ESP32-U4WDH. 2 MCUs communicate with each other at 12 MB/s for months without any errors. One of MCUs communicate with ESP32-U4WDH UART1 at 1.25 MB/s and each time I pause a communication for 5 seconds or at the startup, the first received bytes are incorrect. Most of the time, they are the same, but from time to time they are different.

If you have any ideas, I can quickly test them in my setup.