Where were these wallet.dat files sitting? in a CD/DVD, HDD, SSD? did you find them and one of them was corrupt? or did you accidentally delete a wallet.dat? Are you on Linux or Windows? Are they all BTC wallets or some altcoin wallets? (you mention LTC)

If you are on Windows you can use recuva:

https://www.ccleaner.com/recuva

In Linux look one of these:

https://alternativeto.net/software/recuva/?platform=linux

Deleted files are accessible the faster you try to recover them, otherwise if they become overwritten by other files it's over, maybe if you have access to really sophisticated forensics stuff you would still have a chance.

And be sure to know that the wallet.dat you are trying to decrypt corresponds to the software you are using otherwise that's why it may be crashing.