Explorer showing duplicate files/folders on a network drive

I have been having the same issue. Windows keeps doubling and tripling the files and folders in the mapped network drive. It has been after some Windows update that Windows Explorer started that thing. Now you can notice that Windows Explorer is regularly updating the view in the open window. On those view updates the content of the current folder is re-listed. Then sometimes everything is normal, sometimes the entries are doubled, sometimes even tripled. Manually refreshing the view (F5) works similarly - sometimes single entries, sometimes doubled. Interestingly: if Windows Explorer is automatically refreshing the view while you are renaming any file/folder, it throws you out of renaming and shows again the old file/folder name, so you can begin with it again.

What else could be seen is that Windows Explorer confuses paths. Let's say you have two files:
Z:\a_folder\b_folder\c_folder\d_file.abc
and
Z:\k_folder\l_folder\m_folder\n_file.abc
but for a short while (probably on those strange view updates) it mixes it up to a random thing like Z:\a_folder\b_folder\m_folder\n_file.abc
I realized this thanks to my backup program which throws out errors that those mixed up paths do not exist. That's understandable of course. However it seems that after a while (maybe a second, maybe shorter?) everything is back to normal again.

It seems as if the doubling or tripling of folder content is connected with the mixing up of paths. Both happen quite randomly (but always on that refreshing of the network folder content view) and repeatedly for short moments. That's why F5 usually works (as usually being hit a moment after Windows did its thing). The issue however keeps coming back.

BTW: I am also using a FRITZ!Box. Tried it with a 6660 and a 6670. Both the same! Coincidence? 🤨