After hours of tinkering I think I found the secret sauce! I set them both to remove their sickness state, by editing these stats for the followers:
"CursedState": 68, TO "CursedState": 146,
"DiedOfIllness": true TO "DiedOfIllness": false
"DiedOfOldAge": false, TO "DiedOfOldAge": true,
146 is the standard death from old age state, rather than 68 which seems to be illness that is casted on them (pestilence).
Flipping the DiedOfIllness and DiedOfOldAge is just for continuity.
Upon doing so, I was perfectly able to resurrect solartech0. I'll test to make sure I can res TheSilentSymphony. They still both show as sickly faces in the Rituals menu, so it definetly isn't a clean fix, but I didn't encounter a freeze!
Lastly, I also removed the same pestilence curse from the other surviving followers [ "CursedState": 146, to "CursedState": 0,] as a just in case as I'm not sure if the event causes the ritual freeze or maybe its the sickness itself, or maybe the event + the deaths[I think it's the latter.] Like you said, a lot going on in my save. (This is also likely because I'm playing 100% with twitch integration, been super fun so far!!
I'll have to do more testing/gameplay to make sure I'm in the clear though, but no freezes on my side is a good start.
I attached my edits just incase anyone else wants to take a peek. You can compare with my previous save from the page prior.