The FR5 diagnostic viewer stalls when its log folder is busy. It is separate from cell controls. I suspect synchronous writes, but communication delays are still on the list. More logging has become a rather circular suggestion.
Time the read and the write separately, then replay saved responses with a controlled slow writer. Test a delayed read separately too; a frozen display can be the same complaint with two different causes.
Saved-response test reproduced the stall with a slow write and an immediate read. The developer is moving logging off the display path with a bounded queue; full-queue and read-timeout behaviour still need testing.