I have a modified version of the RTC_Clock example and it doesn't wakeup after an M5.shutdown(55) when it is connected to USB. If I disconnect the USB cable, the sketch works.

The same behavior when I use the unmodified example. The RTC_Wakeup example also exhibits the same behavior.

This makes it impossible to use Serial.print debug statements.

Happy to include my modified sketch when I have the privileges to do so.