I'm guess it is the motor on the latch? This happened around 18 months ago (middle of the summer) and then seemingly the problem went away so I didn't investigate further - not sure when it returned exactly though.
There are a few used parts on ebay - I think the part I need in the middle of the 3 pieces - presumably it can be disconnected form the interior door handle (right) and the left part (inards for the external handle?)

I'm wondering if I remove the door card whether I can manually lock the door until I find a replacement part?
Is that same part used in any other PSA cards so that I can possibly cast my net a little further - the part number would be helpful.
Anyone else had this issue?
Thanks.