I know this might be stupid question but are you installing SPT in the original EFT folder or a separate folder?
SPT does delete _BE from SPT folder.
I am installing SPT into a separate SPT-AKI folder which I have copied the contents of my original EFT folder to. Then running the Launcher from inside the SPT-AKI folder. The game opens and closes and the log files say "EscapeFromTarkov_BE.exe file not found"