P: Can't import videos

When importing, I uncheck the videos, however, when syncing the folder there is no way to exclude videos. Since the folders change as the mobile device takes new photos, I have to sync the folders, instead of importing.
The sync hangs, when cancelled this is the error message window. However it is an unknown error. It would be good to display some errors to be able to track down the source of the problem...

The videos are mostly taken by Samsung Galaxy J5, so a kind of standard format...

This is great. I just tried the new version and imported two videos which previously drove LR crazy, and they were imported perfectly well. GREAT JOB!  Thanks a lot.

Version 9.3, an update to Lightroom Classic, went live on June 15, 2020 and contains a fix for this issue. Please install the update and respond back if it does not cure the issue for you. Thank you for your patience!

My mistake. I think I imported from \DCIM  instead of the root. MP4 files show up if I use the SD card root. Live and learn.

I wrote a Python script to check that everything imports to the right place, but I had to use file creation date rather than EXIF data as raw files don't have EXIF. So it's not ideal.

This problem reappeared when upgrading (!) to LR Classic 9.2.  Import process hangs, no way to play videos afterwards.

Apparently there are some videos that cause the process dynamicmediaserver to take up 99% of the CPU and the whole import process hangs.

Probably the trouble are very short videos, such as iPhone Live Photos (.mov), as mentioned by Megan Bromley three posts above.  Somehow some iPhone live videos cause the import process to hang.

Once that happens, no other video in the catalog will play, and of course the import process fails.

If I force quit dynamicmediaserver and restart LR all catalogued videos will play again normally. But trying to import or synchronize any folder containing these "damaged" videos will cause the behavior described above again.

The same happens in Adobe Bridge.

Thanks to Megan's comment I was able to zero in the video to blame, in my case. It was one of the shortest videos in the folder. What make me suspicious was that QuickLook was not able to show movement when playing it (the image froze but the audio plays. So it is indeed "damaged" somehow. But neither QuickLook or QuickTime or any other DAM programs hang or fail to reproduce them. Lightroom does.

After I deleted the video from the folder, I was able to import the folder normally.

Please fix this. I can provide you with the video which causes the problem, as I am afraid that several other iPhone Live Photos will cause the same effect - and it was a nightmare for me to figure it out and to work around it.

Please, if there is a video that dynamicmediaserver cannot process, ignore it and continue importing the remaining videos instead of hanging the whole thing, and issue a message mentioning which video causes the trouble and why. I almost cancelled my subscription because of it (it drove me crazy), and generated several hours of wasted time. And, if not fixed, I am sure it will happen again.

Thanks a lot. 

Exactly same behavior here, running LR Classic 9.2 on a Mac.

On my Sony RX100v7 I took some video of my 87 year old father telling family tales. They were not imported by Lightroom along with photos from the same card and same time. I forgot about them and reformatted the SD card later. I ran the latest version of SanDisk RescuePro but to no avail. 

I just rerecorded some example video and it goes into the directory \PRIVATE\M4ROOT\CLIP as MP4 files. 

There is nothing like emotional trauma for changing behavior, so I will definitely change what I do with SD cards. I will probably write a Python script to check that everything interesting has been uploaded via LR.

It would be nice if LR popped up a message after the import to say which files on the SD card it ignored.