Sometimes item scanning does not happen correctly and fails to complete quests. This was fixed in 4.15 but 1.7.1 downgraded from 4.16 to 4.14 to fix the gui looping (I assume) reintroducing the quest completion bug.

4.17 fixes both the gui issue and the inventory scanning issue.

fixed in 1.8.0 release that released today by updating to latest ftbquests