Urbackup VirtualBox transfer problem

Hey, i have oracle VirtualBox running Win7 PRO x64 VM and there also runs urbackup client 2.0.36. I have a problem with transfer speed. After my VM restart i get 40-50 MBit/s speed and after 3 or 4 minutes speed goes down till 1.75 MBit/s. When restart again it goes 40-50 for 3-4 minutes and goes down till ~2 MBit/s.
Anynone has any ideas for my issue ?
Thanks for your answers.

Does it stay at ~2MBit/s for a long period, or for only about maybe… 10-30% of the backup time?

Are you running AV?
Do you have run Urbackup in background enabled?
Are they very large files?

So, is UrBackup a VM? If so, is there a software speed limiter setup somewhere?

Double-check your server settings; I know there was a time when the backup speed was set to [blank] and after an upgrade it was changed to 1%, you may need to change that value to 100%, or see if [hyphen] ‘-’ is an option for you.