I recently moved my Indigo to a new iMac 24. At the same time, I upgraded to Big Sur 11.4 from 11.3.1. Since moving, my modem has been locking up every few days. It will turn red with a strikeout line through it and the only fix is to reboot the machine. Shutting Indigo and restarting the program doesn't fix the problem.
I keep a spare modem and swapped it out with no improvement. I have also made sure I am running the latest version of the FTDIUSB (believe it is 1.4.7). Indigo version is 2021.1. I didn't think to get a copy of the event log before re-booting to see where the lockup is, but if this is not a known issue with a solution, I'll grab the log at the next problem.
Thanks, Keith