When starting a webengine based example from a network share then it will fail to start the QtWebEngineProcess.exe. This is due to the sandboxing as turning it off with QTWEBENGINE_DISABLE_SANDBOX=1 makes it work fine.
This can be reproduced by setting up a network share on the Windows machine itself and then accessing it as if it was deployed via that share. So no actual external share is needed in this case.
Also, if QTWEBENGINEPROCESS_PATH is set to a copy of the exe that is not on the network share (i.e. with the drive letter etc) then it works fine too.