Sorry for taking so long to respond.
I'm glad you were able to resolve the issue, as I was getting nowhere in my testing. And I think I lost some hair trying to duplicate the issue.
I have the same model recorder and firmware as you, but not the same Graphics card. But I could not reproduce the error. It's possible the firmware upgrade resolved an issue between the recorder and the graphics card, and possible even our software, but I'm not sure how at the moment.
I've not yet upgraded to the latest firmware as you have. I'm still going to try and obtain the Graphics card you have to see if I can get to the bottom of it just for my own knowledge.