Another factor that could be a reason for the behavior, and happens even with a local disc, is how promptly (or not) MC updates a view when the contents have changed, such as a smartview of files selected by tags, or an Explorer-type view of all files in a particular folder. Both types of MC views are slow to be updated when a file is imported, manually dragged in, or has tags updated, changes that should cause the file to appear in the view, but...
In my experience over several versions of MC, updating a view based on such changes can take several minutes, and sometimes doesn't seem to happen at all unless the view is exited, or changed to a different top-level view, then back again. Or wait, and wait, and wait. Often there's a notable time gap.
The issue is proven by viewing the underlying folders outside of MC. The new or changed file is there, but MC is not seeing it and/or not updating the view for quite a while, so long that it is often necessary to go look at the folder to be sure the file is really there. This is a big thing for me because I frequently work at the files level (lots of ripping, editing, etc). To maintain sanity, with two monitors, I have a file explorer open on one monitor, and MC on the other, so I know physical reality vs. what MC shows.
But it is not just physical vs. view, it is a delay updating smartviews when tags change. Typically, looking at new files in an MC Explorer view, I add some tags (Artist, etc), then switch to a smartview that should show the new files (often a sub-level of a top view of all Artists). The new track is NOT there even though the file is there and has the necessary tag. Eventually, it appears, but the delay ranges from confusing (is it really there) to annoying (I need to continue working on it, but I don't see it).
Pressing F5 in MC to refresh the view does NOT help. Why not? I realize it would not be wise to have MC constantly checking for changes. But shouldn't it respond to the user?
The MC view eventually catches up with reality, but a view update doesn't seem to be a particular elapsed time, I've waited 5 seconds, a few minutes, or several minutes before the file appears in an MC smartview. Drives me crazy at times. Perhaps view updating is on a fixed (but invisible) internal schedule?
I've reported this a few times as an anomaly but after a few years it remains. Makes sense that auto-refresh is periodic, but ignoring user F5 presses seems like a bug...
My point is, when trying to sort out Import and other drive/folder/file/tags changes, it's tricky to compare what physically happens to what MC displays.