Take the floor bezel/cover bezel off and look at the condition of
the pawl/ramp that the shifter lock engages. Might be worn.....
it's not a close tolerance part by any means though.
As the drill sergeant said, "I taught you everything you know. I didn't teach you everything I know."
"Human beings, who are almost unique in having the ability to learn from the experience of others, are also remarkable for their apparent disinclination to do so."
- Douglas Adams