Vst location and problem vst2 / vst3

Lately i have trouble opening project i am working at
It happen pnly with project already developed, not with a fresh one
When in Loading mix console, it stay a little while and then everything close with no other sign
I have tried to rename all the vst folder,both vst2 and vst…but still it is not clear which one is causing trouble. For sure if i disable all plugin it opens
Now, i see i have some vst with a dll in the vst plugin folder, and also in vst3
How it works this? should i have only on vst or in vst3? They myght conflict if both are in cubase?
I suspect this might be the cause…at times it opens again other not anymore, and even for this the troubleshoot is not easy

thanks for help