Since nobody reacted until now, I will give it a try.
First, please describe your problem as precize as possible and try to use a written language that also people from outside the US will understand easily.
Reading your post I was tempted to make a joke about the Bermuda Triangle Syndrome, and others didnīt jump in for help because one has to guess what your problem may be.
No aircraft "disappeares" out of the sky or your schedule without something you were doing first to make it disappear.
Could it be, that some of your leased planes just went back to their lessors, because you cancelled the possibility of automatic renewal for them?
Could it be that you leased not from system broker, but another player who limited the lease and didnīt let you renew the contract?
If you turn off automatic renewal of leases, there are possibilities in "settings" to receive a warning prior to soon ending lease contracts that gives you time to look for a substitute.
Hope we found the cause of irritation.