There are numerous posts in the Peoplesoft solution center regarding commit fails. Next numbers & a duplicate unique key id for F4111 is a large culprit as well as bad data in the item master, item cost, or item branch files. I have seen User Grid Overrides cause this to happen in earlier releases on OneWorld. If one User is the culprit, it could not hurt to delete all of their custom grid tabs & then reenter them.
One last idea ... if you have session time outs set, this could be the culprit. The commitments are done as a background job when you exit some of the inventory programs. If you process large sets of transactions (100+) then perhaps the process is not finished before the user gets signed out.
There is a commitment recovery program P42210 which does reset the quantities for you. There used to be a really good knowledge document about this program. I think there is a UDC table that has to be set to turn this on.
Heather