@grimsoul, it's quite random too. I've had a couple of sims where the relationship has changed like normal and a few others where it has just become stuck at impartial despite a nearly or full green relationship bar.
I actually have been mucking around with mods and CC over the last week or so but I've taken everything out, repaired all the games (thanks for the tips about repairing each title), emptied the cache files etc and this is still happening. (Side issue when you repair The Sims 4 main title it will cycle through all the other titles etc in turn anyway)
*edited: I've also had a few sims stuck on 'acquaintances' now too when judging by the green relationship bar they should be good friends.
