Hello, DaveD
Thank you for your reply.
as your mention, glitching on the TMDS signals could also cause this kind problems.
as this problem occure, TMDS_PLL_lock status is locked and Free run bit isn't active.
the output seems to abnormal can't be detected by video processor.
It should be caused from glitching on the TMDS bus during plug and unplug.
I will please software engineer to check more status for reference as STDI funciton check.
Jerry