I have noticed this for a while and expected someone else to report it but still not fixed, so I guess I can only blame myself for not reporting it earlier.
With PMDG 777-300ER, when getting catering services, they open the R2/5 doors fine, load the catering, but then the sim keeps prompting to close the doors. I think what's happening is both vehicles are toggling R5 which means it stays open and you keep getting the prompts.
When you manually close it, the rear vehicle descends but then the door re-opens (I assume from the forward vehicle toggling again), so then you close it and finally that vehicle departs also.
I have just moved PCs so this has happened on two completely different installations.