Hey Paul, I ended up resolving this, a bit of a facepalm moment.
We run P4 locally, Parallell sync/pull is supported, but parallell submission is not on Windows.
When reviewing the documentation, I noticed a random config value at 9. Unfortunately, they don’t mention this limitation on the parallell documentation page, and it is only briefly mentioned as a fotonote on the p4 submit docs page.
I was not aware my local server would be considered an edge server in this case, but just disabling parallell submissions worked. We can still do threaded sync’s, and the virtual asset’s work fantasticaly. Even with large latency, the whole process has been so smooth since. Thanks for your efforts!
So, tldr, p4 bug. I think perhaps the output could be a little more detailed though to indicate if a failure is occuring and it’s not because of the virtual system or as a footnote in the docs for those on Windows.
https://help.perforce.com/helix-core/server-apps/cmdref/current/Content/CmdRef/p4_submit.html
Important
Limitation: Parallel submit is not supported from an edge server if the commit server is on a Windows platform. In this case --parallel or automatic parallel processing for submit will be silently ignored, and the submit will run without using parallel threads.