Imported files get duplicated when document is loaded

[j-maas]

After adding a second video using "Import Data", closing the window and reopening the document, I can see in the "Linked Files" window that the imported video appears twice. If I reopen the document again, it will double to four.

This affects playback, as after a few reloads the sound from the imported video will sound roboter-like because its sound will be played multiple times simultaneously.

Apparently, when the document is loaded, the linked files get redundantly re-added.