I bought a used IS350 at the beginning of the year, had it shipped up from Texas because it was the right drivetrain (RWD) and color (matador red). Left rear door lock started intermittently not working after a few months of ownership, Covid also started so I decided to deal with it myself rather than bring it to a dealer. In August it stopped working all together, so I jumped on here and realized it was likely the door lock actuator. Ordered my part in late September, and finally took the door panel off yesterday. The original door lock actuator was simply unplugged. I plugged it back in with a resounding "click" and tested it and it functions properly.
The door panel doesn't appear to have been opened up since it left the factory, none of the door plastics were marred, and the inner weather seal still has the original sealant on it.

I'm glad it worked out, but perplexed as to how this situation unfolded. Some time prior to my purchase the door lock actuator wasn't fully plugged in, and eventually came out completely - could have been the trip up from Texas that did most of the jiggling, could have been my 6YO (or wife..) slamming that door all the time that did it; either way, glad it's back to functioning, now onto more (mostly appearance) mods. Oh does anyone happen to have a spare 2018+ F-sport RWD LSD sitting around they don't need? I'm asking, for a friend...