I've never had to replace those, but maybe some food for thought....

Use some orally applied natural grommet lube (spit) when installing them. It might help the seal settle in to the proper groove.

Maybe try putting the seal down into MS first, then "lube" the barbed tips on the reservoir and push it in. My thoughts are that installing the plastic part last might be less likely to tear the seal than the metal edges of the MS if you try to push them in to the MS with the seals already stretched over the barbed tips.

Aren't the barbed reservoir tips tapered on the end a little bit to help them slide down into the seals?

Good luck.