Crashing in cubase

Hi,
I hope you can help as I have been facing similar issues for some time now, but in my case the Asio Guard is off. I am using Windows 10 and Cubase 10.5. I can start Midi Guitar but most of the time no sound and signal can be heard/seen. Strangely enough, sometimes it does work, but only 10% of the time. I cannot identify why it happens. I followed every steps in MIDI Guitar & MIDI Bass Support – Jam Origin, reinstalled twice, but that made no difference. I also noticed that when I have Midi guitar loaded in a project, Cubase crashes when I load the project, unless my buffer is at max. On the opposite, if Midi Guitar is not loaded in the project, Cubase runs smoothly.
If anyone has any suggestion that would be great!
Thanks,
Jules