The same thing can happen in original Scenario, because I see that this is also wrongly defined there. You can try latest beta, michelm already tried several times to fix it, but I am not sure it will fix itself, if it already happened.
If you want to change database, it can be little complicated. It is generally because device is in different slot in LCU definition, and its TOE:
1) click LCU in game, and you will see its number in upper-left corner. This is exact slot in LOCATIONS tab in editor.
2) in editor check if fields TOE ID, and Upgrade TOE have any numbers. If they have you have to also check those slots, as problem can be in model unit.
3) click Show TOE checkbox just over list of LCU Devices. It will show desired TOE, and you will see, that Support is in the place of MMG, this is cause of problem. Just change Support, and MMG devices in places, so all Devices in TOE, and LCU will be in the same slot (of course, you have to also change numbers on the right).
4) this unit is part of bigger unit, which have Devices in even different slots. This can also create problems after merging.