Whaaaaaaaaaaat? That's crazy! How? I have my music tags broken down into the bare level of Album artist, Artist itself, track #, disc #, and nothing else. No art, no genres, nothing. Is it maybe just a bad card? Should I try reformatting it? Remember, it is set in FAT32 format because that's the only format my car USB device recognizes. Maybe it's that?
Edit: It's a Sandisk Ultra Plus UHS-1 64GB class 10 card with an 80MB read speed, if that makes a difference
There's just so many things that can result in media files doing stupid things. It may or may not be the card's format. It may be card fragmentation. It could be that your encoding software places the metadata at the end of the file instead of beginning. It could be that you're copying the files via the player and not a card reader. There's just so many things that can be "off".
I had tried both FAT32 and exFAT on my first 256GB card to see if there was a difference. I noticed that with FAT32, repeated copying and deletions slowed the card down a bit as it neared full (allocation table fragmentation was probably the cause). exFAT did not exhibit this. So I stuck with exFAT.
I've never formatted the card in the players, always in the computer. I use a Lexar USB 3.0 card to take full advantage of the card's speed.
When it comes to file tagging, some encoders/taggers/editors don't support standards completely. If you have MP3s, be sure that they are tagged with the older IDv2 2.3, not the newer 2.4 which has issues with a LOT of players. Also, I'll strip out APE format tags. FLAC uses the Vorbis tagging system, which has quirks too in some implementations. All of my files have between 500px - 700px covers. All file sizes are less than 100K, mostly closer to 40-50K. The cover images are optimized in Photoshop using "Export for Web". They are all saved with JPEG Quality around 70%. The same cover image also is placed as a "folder.jpg" in each folder - note that I don't use the new standard "cover.jpg".
I also have the habit of clearing all tags from a file, then re-inserting the tags myself if I didn't directly rip the files from disc or ISO. I've never had a single file touch an Apple product - so none of iTunes' whacky non-standard tagging crap. And, yes, Apple products have a lot of non-standard "standards". As a photographer, I've had to deal with some idiots sending me Apple exported JPGs that are whacky because they couldn't export it in sRGB and was encoded poorly, but couldn't understand why the image "didn't look like it that on their screen". Of course, they didn't calibrate their monitors either "because it's a Mac and doesn't need that".
I have a Kenwood Eschelon player in the truck. It uses a USB FAT32 format. I have MediaMonkey convert to MP3/320 for it on export when I do a device sync, specifically for the truck. I don't "share" files between my FLAC player and my car's head unit. It has it's own 128GB Sandisk Extreme that never gets re-imported into the system (one-way data path).
I also be sure when tagging to remove any UTF characters from tags (even though Vorbis supports it, doesn't mean that the player may have the character set). I also manually rename the file in MP3Tag to match my metadata. I use a script to check for non-ASCII characters in both and convert them to underscores. Each one of my file names match the metadata exactly and are in the same format (Track#. Title - Artist.extension).
All of my FLACS are converted using the newest FLAC lib to Level 6. Any MP3s are 320K CBR joint stereo. DSD files are in SonyDSF format.
So, it's really hard for me to guess what is causing yours to update the library and function slow. My suggestion is that you copy your card off to your computer (or if you are syncing, just format the card). Then, copy over about 250-300 files and test them on your player. Time your library update. Then, start eliminating variables and find the cause of your slowness. I'll tell you that it's not the card speed, as I have a half dozen cards from 256GB to 64GB (Sandisk Ultra/Extreme, PNY, Samsung) that all work smoothly on read via the player. The only difference is the copy speed TO the card, which only makes a difference if you are utilizing the full potential of the card by having a fast card reader (I dump 256GB CF UDMA7 cards from my camera all the time, so that's a requirement) using USB 3.0 (USB 2.0 has a 16-18MB/s limit), and a fast computer (my files are coming from a 8 disc SAS15K cluster in RAID6 with a 2GB cache to take full advantage of the pci-e bus speed to a Startech PEXUSB3S44V dedicated port USB controller) to keep up with the card.
Yes, the player can have some lag, but never more than a second or so. And that is usually when it's opening a 24/96 FLAC file.