i have very similar problem with my 5200HC non SpeakerLink.

I got some symbols after switching on.

l can’t upgrade it to 1.4 firmware from 1.1.

I upgraded DSP7000 to 1.4, but upgrading 5200 failed after several minutes.
what can be the reason?

https://www.youtube.com/shorts/utwqG1Xe-uM?feature=share

HD621 , 800v4, 861v4, DSP7000, DSP5200HC