I know I'm jumping into this party a little late but I got the "willies" when I shoved in the fob to a beautiful '08 XC70 non-turbo (w/46K) at a local gas station.
The bladeless fob gizmo inserted a bit and pushed itself out.
The seller told me just to shove it in. It responded but I felt I was revisiting the days of a finicky cassette player.
SHAME ON VOLVO for being cute.

Servicing battery terminals IS NOT a superficial job.
Mix up a paper cup of baking soda and water and dunk the entire battery clamp into the slurry. You can always tear the cup to accommodate the cable's length.
Remember to brush the underside of the clamp too. Don't stop 'til it's 100% clean.
Clean the battery's posts with the same slurry a suitable brush.
RINSE
Then get a spray can of BATTERY TERMINAL SEALER.
Tear a wee hole in a paper shield and spray coat the post.
Apply the clamp and spray it too.

Sears-Roebuck (of all places) used that stuff on a battery I purchased and there was NO CORROSION over the life of the battery. I won't service a battery without it. I don't care if grandpa used moose fat or railroad grease.

Clean every ground you can find.

Unforgiving power supplies have been the rule for years now.