@Yordan5
I'm amazed that you only got 3.5 hours at that compression!
Why do you compress that much? Please explain?
If this was an BD-RB issue there would be lots of posts here.
You could use this tool to enable/disable “Meltdown” and “Spectre”.
Check if you have protection enabled, if that is the case disable it.
Reboot your machine and do a new encode.
You can then enable “Meltdown” and “Spectre”.
https://www.grc.com/inspectre.htm