Show/Hide tracks memory locations getting corrupted?

[clutch]

Hi, it's not often I'm at my wits end with a PT problem, but this one has me really stumped.

I have an issue where my track show and hide memory locations are off by three tracks after I close and re-open a session.
That is, if I have set memory location A to show tracks 1,2,3,4 and location B to show tracks 5,6,7,8, they work fine until I close and reopen my session, when suddenly memory location A show tracks 4,5,6,7 and location B shows tracks 8,9,10 and 11!
These are just examples - it's happening on many, many tracks.

I made a new session and imported the tracks from the bad session - issue still persists.
I trashed PT prefs, restarted my computer and the issue persisted.
I created new tracks and copied the data from tracks 1,2,3 and 5,6,7 onto them and things were fine again. Closed and reopened the session without issue.

Went home last night, came in this morning, fired up the session and the issue is back.

I don't want to have to make new tracks for all the offending tracks again as there are a lot of them, and updating the many memory locations I have with all the different track views takes a while, and it's not something I want to do every day.

Any ideas as to what's happening?

PT2018.4 OSX Sierra 10.12.4