If the train operates fine, then they are coupled correctly. I would use a cotton swab or other small applicator and put some silicone lubricant on it. If you have forcep clamps, you can also attach them to both couplers and only pry them, not pry by the train.

Thanks for suggestions. I will try decoupling them over Easter as I want to add a carriage that is compatible with this model.
I think this ICE will be added to my permanently coupled collection for which l make individual wooden bases and attach old M track that is used for storage and rolling on and off layout.
Maurice