Off the top of my head I have seen units being teleported because tiles are incorrectly linked.

Often animations get stuck (until a timeout is hit after ~30 seconds).
Sometimes units can appear on a city that already has a unit and is blocked from moving away which prevents ending the turn.
Sometimes linked units don’t move together properly until the next turn.
Capturing a builder or settler with a linked unit just deletes it.
Currently if you buy Gathering Storm DLC you cannot play it with anyone who doesn’t also own Rise and Fall.

And those are just the issues I noticed personally this week.