Cargo planes on passengers gates
I have noticed planes such as the Cathay Pacific b747-800F Freighter not parked on cargo position, instead they are placed on normal passenger gates.
I saw this on the payware scenery Fsdreamteam KLAX
You need to then assign the cargo plane's Parking ID to the Parking Spot using an external program that will allow you to edit the FSDT LAX parking codes assignment. This is an issue with Addon airports as almost all cargo locations are already assigned.
I personally don't have that problem with LAX but do with other (standard) airports. You just have to make sure you have enough unassigned Cargo area gates that are big enough for said crago OR assign the parking codes.