OK, had the bug pop up again. Things are a lil different now than they were in the past because now I have a household with more than one Sim in it. I usually play single Sim households but have had the bug pop up before in the past with multi-sim households but that was before I had figured out my work around. What I noticed this time around is that when the bug pops up, it occurs to every Sim in game- even unplayed households. When I noticed the bug popped up, I went and checked if the other Sim in my household had it too and they did. I then went and checked with another played household and then an unplayed one. Sure enough, everyone had it. I then started up my "fix" with a single Sim in the household I was playing. This time when I tried my "fix", the Sim in the locked #1 position jumped to row #16 in the panel, quite a ways down my list and further down than when I play with a single Sim. This time when I talked to the Sims progressively moving up in my list, I noticed the initial locked #1 position Sim wasn't moving much. It moved from row #16 up to row #14 then stayed there. I kept up with the invite over and talk to operation and after a while noticed a Sim I had already talked to during it was moving back to the #1 position. When that Sim worked its way back to the upper right #1 position a second time, the bug cleared up.
When I checked the other Sim on this household, their relationship panel is still bugged and locked ☹️ I may at some point check and see if the "Fix" works on them too but after calling up and inviting Sims over for a solid 10-15 minutes or so I'm not really feeling like doing it again anytime time soon. Perhaps after a while it will fix itself for them and the other Sims in the world like it has before in the past for me. It's a really weird bug. No idea what starts it but when I noticed the bug popping up again, there were two events that occurred before the bug popped up. I may have missed exactly when it popped up. I haven't been checking the relationship panel every time my Active Sim talked to someone. Now these events might be total coincidence and not related in any way to the actual bug starting up, but they were two possibilities I noticed before the bug showed up again. 1) I was thinking maybe the number of Sims in your relationship panel triggers it when you get "too many" Sims in your Relationship Panel. When I noticed the bug I checked to see how many Sims were in my Active Sim relationship panel. It was 79, one less than the 80 Maximum Sims I had set in the Manage Households in the manage World Screen. I went and bumped the Maximum Sim Count to 200 then went back to the household and the bug was still there. I don't think the Maximum Sim Count triggers or affects the bug. At the least bumping the Count up doesn't fix it if it does initiate the bug. 2) I had a related family have kids right before I noticed the bug popping up. Again, might be total coincidence but those were the only two things that stood out from day-to-day gameplay I noticed before the bug popped up again.
That's it for now. Might message back if the Relationship Panel fixes itself for the rest of the Sims in the world. I might try and fix the Relationships for the second Sim in my Active Household and see if that affects anything. This bug is a weird one. I just wish I knew what causes it.