I recently bought a box set of 4 Blu-rays containing recordings of all Shostakovich's symphonies and concertos, plus a documentary film. I was pleased to find that MakeMKV displayed each work in a separate folder, so I ripped the discs into 22 separate MKV files. I scanned the front cover of each Blu-ray and placed a copy of the relevant jpeg in each of the 22 folders created by the ripping process. I then used MC's 'Cover Art > Quick Find in File / Cover Art Directory' to associate each MKV file with the cover art image.
My problem is that if I choose the 'matrix of thumbnails' mode in JRemote on my iPad to display all of my videos whose Genre setting is 'MUSIC', it doesn't always use these new cover art images (it uses thumbnails taken from the first frame of each MKV file instead). However, if I use the display mode that places each item on a single line with a thumbnail on the left hand side then the correct cover art is shown. Selecting an individual MKV file also always shows the correct cover art.
Rather oddly, only the 6 MKVs associated with the second of my new set of Blu-ray discs (BD2) are affected in this manner. All 16 other MKV files display the correct cover art in all situations. There are 6 copies of the same BD2 cover art jpeg file, which is is almost identical in size to the jpegs for the other 3 Blu-rays (800 x 1124px, 168KB).
I've tried reopening the BD2 jpeg in Photoshop and resaving it after making a trivial alteration, but this made no difference. Stopping and restarting JRemote also failed to resolve the problem. Neither did switching the iPad off and on again.
Is there some magic trick to make JRemote reliably update all its cover art thumbnails or could there be some obscure problem affecting my BD2 cover scan jpeg?
EDIT: When I look at a thumbnail display of all my Genre = 'MUSIC' videos in MC 26 then all is well. All thumbnails in Gizmo and the Android version of JRemote are also fine. My problem is purely with JRemote on an iPad. I'm using JRemote 3.34.