USART1 Interrupt priority

[Gregwar]

I'm currently working on a project, and I needed to read data contiously from Serial1

My computer opens the USB ACM port and give some order to the board which starts talking very often to Serial1, which means that a lot of "RX" interrupts happens

If I close and open the USB ACM port, and if an RX interrupt on Serial1 is happening, it seems that the board just crashes

Changing the uart priority to 0 seems to fix the issue but I'm not sure about what the problem is exactly