Cannot run CDB when PYTHONPATH is set

If the PYTHONPATH environment is set, QtCreator is unable to run CDB (qmake project).
When starting a debugger session, the following error message is displayed : "The CDB process terminated".
That's odd, because if I disable "Python dumper" in Tools > Options > Debugger > CDB, it doesn't change anything.
The debugger output doesn't contain valuable information to solve this problem (see attached file).

As a workaround, it is possible to : go to the project tab > build environment > PYTHONPATH > disable.
Other people having the same bug :
https://forum.qt.io/topic/69130/unexpected-cdb-exit
https://stackoverflow.com/questions/49638891/qt-cdb-crashes-after-setting-pythonpath

Happens with Python 3.6 32bits (while debugging a 64bit program with cdb x64).
Happens with Python 3.9 64 bits (latest).
It may annoy Qt for Python developers.

Can you setup a better error message / debugger log, or resolve the problem ?

Thanks a lot.