macOS Mojave - Failure w/thumbnail cache same problem with High Sierra

Today has been annoying me so much, simply trying to sort movie files and I just get the beach balling for so long, I even went and spent £90 and upgraded the RAM to see if that would make things flow faster but no luck, this is getting really stupid, it's the same issue as when High Sierra came out so they should get a fix for this ASAP! none of my thumbnails show up, my custom ones don't show, I can hardly do anything in my folders as I get the beach balling and I can't click anything, you'd think with people spending thousands of pounds on Apple products they'd get a system that actually works correctly.

Hey, appreciate you sticking with this issue enough to get not only an actual response from the support team at Apple, but also what seems like a followup?

Still amazing that this exact same issue plagued both the beta versions of High Sierra (and was reported both here and to Apple) and ended up in the shipping version of High Sierra (and was reported both here and to Apple) and then was actually addressed in an update (which was pretty cool), and now we are going through the exact same cycle in Mojave. I guess the hopeful good news is that Apple did get the message last time. The frustrating thing is they repeated the same problem, and it doesn't give me a lot of confidence for the next MacOS update.

Also, I will be the first to admit this is not a mainstream type bug-only those who use custom icons and external drives experience it. But it is absolutely a debilitating bug in terms of functionality-grinds the Finder to a halt.

I still have the exact same issue as I did in High Sierra, which you've already state, was fixed with an update, and to have the exact same problem again with Mojave is so annoying!!!

I'm trying to sort out my movie files, which i've spent countless hours sorting custom thumbnails for (the actual movie covers) using the Image2Icon app, and I just opened my 'N' folder which has all my movies in beginning with N, and i'd say it's been open now about 5 minutes and it's still very very slowly putting the thumbnails on, there is about 87 files in that folder, and to take this long just to add the thumbnails to the file is pathetic!!! and also then when I click a file and go on 'get info' to add a custom thumbnail to it, I just get the spinning beachball for ages and I can't do much, spending nearly £3000 on a computer, extra hundreds for RAM, and Apple can't even get simple thumbnails to show up! it's driving me nuts.

It's driving me insane today, trying to sort my NAS out, and move movie files from my external hard drive, to my NAS folder via my iMac, yet I click on my movie folder and it just beachballs for ages!! I can't do anything.

I'm in the exact same boat guys and it's been a real pain ever since upgrading. It took me ages to even find out exactly what the issue is but now that it's listed here, at least we can relate that you're not the only ones suffering from it :)

There is no workaround it seems at all. The only way I have found to be even able to work is by not opening the folders with the actual files in them but move the whole folders and luckily, I only have 1 movie per folder so drag & dropping the folder directly into an app circumvents the loading of the thumbnails sometimes....totally idiotic and crazy to see that this has already been fixed before and is now back :(

I really hope this will get fixed once again because working like this is impossible...it's actually a problem I would always watch out for every single time before an upgrade if it comes back in a new macOS version..

Thanks for that, i'm just backing up my files now to Time Machine, sadly I didn't have Time Machine when having High Sierra so i'm going to see if I can downgrade now back to High Sierra, hopefully it goes ok, my OCD is going through the roof though as I love having the newest releases for things and when there are updates/upgrades available and I don't do them, my anxiety kicks off lol but this slow external hard drive stuff is driving me even more insane.

So, went to downgrade lastnight, simply go into recovery mode, go into disk utility and erase the MacintoshHD drive, but, I didn't have a MacintoshHD drive, and wasn't 100% on which to remove and so on, so I went onto the live chat, and finally got it sorted late lastnight, one senior was getting me to erase each internal drive I did have but after doing the first one I accidentally clicked back on my iPhone browser and lost the chat, so I went back on, and the other senior basically got me to go into Terminal first, and create the MacintoshHD and do some other things, and I then had Fusion back with MacintoshHD under it, so everything was sorted that end, so I then went into Reinstall macOS in which it installed Sierra, and then I upgraded to High Sierra, checked my external hard drive with my custom thumbnails and it works perfectly, custom thumbnails show up instantly! i'm a bit gutted due to the fact that I work at night mostly and I loved the dark mode on Mojave :-( it was a lot better for my eyes, but I suppose i'll have to give that up if I want my custom thumbnails on external drives to work as they should!

Only problem I have now, is that on Time Machine, when I drag my files back to the fresh iMac, which were originally on my iMac (not an external drive), they have the custom thumbnails on my folders, BUT they also have an 'icon?' file in each folder that has a custom thumbnail, hundreds and hundreds! and I don't want that, but when deleting that icon? file, it removes the custom thumbnail from that folder :-( so it looks like i'll have to redo all my custom thumbnails on my iMac again!!! the ones on my external drive are fine obviously as they weren't on Time Machine, but yeah, that sucks, and I don't know how I can get rid of those 'icon?' files without it removing the custom thumbnails too :-(

Regarding my movies, I basically download the DVD cover (or poster) for that specific movie, then I use the Image2Icon app, which then enables you to create a icon that looks like an actual DVD case with the cover/poster on it, so basically when I go to my movie folder it'll have images of actual DVD cases with the cover on them instead of the usual file type icon or small player icon, once you create the icon you right click the movie, get info, and drag your icon to the icon part in the get info window, makes it look so much better, and easier to scan through too.

How to Downgrade macOS High Sierra

The above will get you back to High Sierra. The same process works in Mojave if you have a High Sierra backup.

I have the same problem but with so many movies it crashes my system trying to load... I am so upset that I can’t even get to my movies because when I do it crashes.

Also having this issue since the upgrade. Thought I was the only one.

I also have been having this problem, it's becoming a nightmare.

How are you able to add custom thumbnail images for movies? When I add them in Mojave, I'm still stuck with the movie file as a playable preview instead of a static custom image.