Hi,
I've had a catastrophic crash with Launchbox 5.9 that erased all my covers, art, movies and manuals. Sadly, I didn't capture the exact error message at the time of the crash, not realizing how bad it was, but here's my best recollection of what happened. Sorry it's long - never know what clue might be the key to fixing a bug so I want to be as thorough as my sleep-deprived brain will allow. ;)
I have an external drive with my LaunchBox setup (emulators, roms, covers, etc.) so I can move it from machine to machine. After scraping some covers, videos, etc. on my desktop PC I moved the drive to my laptop and launched LaunchBox.exe. I got a .NET-style crash complaining about being unable to find some path. I assumed it was just something to do with the drive letter mapping on my desktop PC vs. laptop - I have the external drive mapped to L: on my main PC, but it defaults to D: on my laptop. I'd run LB once before on my laptop without issue, but I'd done a bunch more scraping/emulator setup from my desktop PC since so I figured it had to do with that.
I closed the crash message, ran again, and got another crash. So I remapped the drive on my laptop to L: and launched again. This time it didn't crash, but all my thumbnails were gone. I checked the folders on the drive and sure enough they were ALL empty - no covers, no movies, no manuals, no nothing.
I closed LB and looked at the config files and xmls for clues, searching through the folders for .jpgs, etc, but no luck. So I tried relaunching LB, and it crashed again - this time no error message, just the standard "LaunchBox.exe has stopped working..." message. I tried BigBox and it launched without crashing. I shut down BB and rebooted.
After the reboot Windows 10 tells me my drive has errors that need to be repaired. I let it do the repairs, and the drive seems to be working fine, although all the scraped data are still gone. At this point I'm thinking, "OK, maybe I've got a bad drive - it's brand new, but these things happen." but then I start searching the forums for similar problems and notice this loss of all cover images has happened to at least one other user on an older LB release. So I think the problem lies with the software.
As a test, I tried reinstalling LB in another folder and that one launches fine. So I copied the exe from the original installation folder and ran it from the new folder, and it also launches fine. But launching from the original installation directory still crashes. So the data it's accessing in the original installation folder is corrupted and LB is not handling it well, I guess.
Hopefully this helps you track down the cause of this bug - luckily I only had a couple gigs of movies, screenshots and manuals to replace, but I can't imagine how long it would take to recover a really large collection.