I have the same issues... its one of the reasons I still have TRS19 and the TRS22 SP3 made things worse for me, with SP3 the game is unplayable im my opinion I am glad I still have an old install (Pre SP2). What I have learned is that when you play TRS22 with a "heavy" session (e.g. lots of AI...
I had the same issue with signals from sessions imported from TRS19, the only solution for me was to bulk update - replace them all with the same signals and save.. that made them working again, it was always the signals at junctions.
The update to build 123801 gave me the tree flickering as...