I tried: gathering the data in the same printf does not change the behavior.
After a search for an error code on the National Instrument forum (LabView) I found that several people have already had a problem of connection loss on a serial port (via USB port or not) depending on the hardware which was used. The only solution I find on this forum is to close and then reopen the port, it works for me but it takes between 0.3s and 2s. this time is long when we want to act on outputs of the L432KC every 0.1s (I even hoped 0.01s).
I will try again without intentionally creating a data format error.
Sorry to have solicited you so much for a crash that comes more from the computer than from the microcontroller.