I rebooted the headset right before doing this and went straight into deovr. It seems to be connected to exiting a video and changing directories while there are still circles on the videos in that folder.
Recreation steps:
1) open deo vr and connect to a dlna server.
2) go to a folder that has a lot of large files in it, aka vr videos
3) while you still have some circles on videos due to thumbnails being loaded, open a video. you can take your time here if you want. the duration you spend in the video doesnt seem to matter.
4) close the video and while there are still circles, go to the directory above the current one.
the size of the videos and the quantity of them seem to play a part here. I tried making a small plex server with video game recordings to reproduce it, but i couldn't.
While the error is displayed, you can't click on anything, but the b button does bring you up a directory when you hit it. That can take you back to the home screen but the error remains until you force close deovr.
Also, one time when trying to reproduce this (with the exact recreation steps above), deovr completely froze, so there are multiple bugs here.