the 1st release of the 1/48 line (hikaru 1a) has the following problems:
wing flaps tend to fall off easily
nose cone not as secure
front landing bay doors are tricky to remove
the 1st relase of the 1s type fixed the wing flap issue.
The 1a max type introduced the following fixes:
rails on the nose cone to make it more secure
design change to the landing bay doors to make them easier to open.
Also introduced is a redesigned head rest on the pilots chair, it now has a curved headrest compared to the original which was flat across.
All subsequent releases of all variants have the same fixes.
The only outstanding QC issue would be on the 1s type occassionaly shipping with skewed skull emblems.
All 1/48's have somewhat fragile back pack hinges, so as many have mentioned, care should be shown with that part, particualrly while installing the fast packs. Though, it's hardly as fragile as some would have you believe. there are several disaster survival stories out there, here's mine: my 1s with fast packs rolled off my dresser and fell about two feet on to a nightstand and the fell again on to carpet, nothing broken.
There are no issues with the gunpod other than the gunstrap being fussy.
So, as long as you're buying re-releases, you have nothing to worry about.