... there was a bug/issue where you could add enough items to any container such that eventually, I don't know if the trigger was number of items or total weight of them, items would disappear from the container. Does anyone know if that issue ever got fixed?...
That issue was never fixed. It cannot be fixed by mods (unofficial patches) since it seems to be in the game engine. Only Bethesda can fix it, and they are no longer patching the game.
The bug is triggered by having items in a container that are repaired to over 100 health (usually 125% health). And then it is not predictable. I've had huge numbers of items in a container with none at over 100% repair and never had a problem -- I use a container for Alchemy Equipment and large numbers of ingredients with no problems.
Even if the items disappear, it's not game breaking. The "Take All" button will retrieve all items, even the ones that disappear. Then you can just replace the ones you didn't want to take, and hope the bug doesn't occur again. That could be tedious but it's a way around the bug.