Nuendo hangs when I an changing track

I have been experiencing this issue with Nuendo 11 and 12.
Whenever, I am changing track, Nuendo seems to hang for some time (easily 30 seconds).
I believe it could relate to my use of VSL pro or the number of tracks in projects, where I experience this problem I have 500+ tracks (primarily midi tracks).
In smaller projects, where I don’t use VSL pro, I don’t experience any issues.
Hardware: i7, 32Mb RAM. SSD disks only.
This worked OK before on the same hardware. I cannot point to any changes I have made that could cause this problem.
The network connection to VSL host is 1 Gbps and transfer rate, when I do large file transfers is around 850 Gbps or more.
Is there anyone, who can help?

Thanks