Deadlock on Windows 10 pop-up

I was able to install and can log in but whenever a pop-up is attempted the VM appears to deadlock.
I can still kill -9 the process and recover but the VM and the QEmu console both hang with no error output.

At first I thought it was UAC but renaming a file causes a pop-up and that also deadlocks.
I rebuilt QEmu 2.6.0 with debug info and did a thread back-trace once the deadlock occurs.
See the attachment for the trace.

I am attempting to setup GPU pass-thru with a GTX 970 but this deadlock occurs with -vga std (and no GPU pass-thru) as well.

(I cannot install or start Windows 7 but I am told this is a known bug.)