Hi,
We still use TMG 2010 for site to site VPN between 2 offices. We have a weird problem where it just decides to block some traffic from only some machines to only some servers in the other site.
If we disconnect the VPN tunnel in routing and remote access, it self-reconnects and all is well again. We're having to do this every few days.
Our environment is 2016 Hyper-V nodes, and TMG VMs are running Windows Server 2008 R2 SP1 and TMG version 7.0.9193.644, which is the latest according to here.
I looked online and I read about a 'race condition' and a problem with afd.sys. I checked and ours are 6.1.7601.18264 dated 9 March 2018 for site 1 and 6.1.7601.17514 dated 20 November 2010 for site 2.