I just sold the last thermolds i have had since 1998. Only issue i had was having enough on hand to sell for a 'reasonable" price to other shooters. if you're concerned about reliability NEVER buy USED USGI mags with black followers.
All mags have some quirks. The last batch of gen 2 pmags don't lock in to ANY AR i have. Sending them back was not an option, so i fixed the mag release cutout area, to have them function.