That's definitely odd. Might try looking at any fuses/relays with descriptions relating to the doors and making sure they're good/clean. After that, maybe sit in the car while running and cycle the interior lock buttons a bunch of times to see if it wears off any small internal corrosion? You can also try the key fob while sitting there after that, to see if you notice more responsive action? Aside from that, maybe manually move the locks a few times, and see if they react better?
These are all just some non-invasive things before diving into any wiring issues, like chasing the grounds for those circuits.
