I have a thread on Reddit here: https://www.reddit.com/r/sysadmin/comments/o0rzt3/in_desperate_need_of_help_with_a_problem_with/
Here is a copy of my issue.
Having major issues.
We have AD on Server 2019, and we also run Remote App with Session Hosts etc. Basic run of the mill setup. Clients are all Windows 10 21H1. We also run WSUS (which is helping my problem be manageable). We also run FSLogix for roaming profiles. For those that don't know, FSLogix uses a VHD file for mounting effectively the AppData folder for the user.
The problem:
We are getting a few updates that are causing a problem. The problem is that the VHD mounts, but you cannot assign a drive letter to it to be able to read it. FSLogix doesn't add a drive letter but seems to mount the VHD (I see the file getting read) but it keeps saying it's already mounted, seems it just can't read it.
The VHD files are on a Synology NAS. The problem occurs on both VHD or VHDX files. I have played with the SMB settings and I have tested on my home PC, that has Synology NAS and WIndows 10, just no domain, but I don't seem to have the issue at home.
The Updates are as follows (for both Windows Server (Session Hosts) and Windows 10:
KB5001337
KB5001330
KB5001406
KB5003173
KB5003171
KB5003637
KB5003646
There can't be the exact same problem with every single update. I am starting to think that something these updates do, is a symptom and the actual problem is something on our network, maybe even a configuration issue. The ONLY thing that I can think of that is glaringly different on my works network as opposed to home, is that here at work we have Multicasting disabled on the network. But I also can't imagine that being the problem.
I really need help working this out. WSUS lets me manage these updates but I am now concerned we will be open to other issues these updates solve. I really need to get to the bottom of this issue. Any help in further diagnosing, and/or suggestions on what to look at next would be much appreciated.