I have the same problem. My HX Stomp was still running the 2.92 update. I connected this wit the HX Editor, tried to update. I got an error and now the screen is flashing like described above.
I tried to install the Lin6 Updater, but miy macbook (macOS Big Sur) won't open it (says it kan scan the program, I need to contact Line6).
Any help here?