OT regarding involuntary shifting:
After 2000 miles, the chain has elongated - and one can measure it. But critically the %age elongation does not matter: what matter's is whether the associated cassette wear has gone beyond accepting a 'new chain'. It'd be worth fitting a new chain asap, without throwing away the old one, and seeing if the cassette will accept it (ie go for a quick test ride and give a good hard push up a gentle hill). If it will: happy days (and make a note to change in another 2000 miles). If it won't: refit the old chain and that chain and the cassette can grow old(er) together, in harmony. (Of course the 'new' chain can be kept to use with a new cassette when the time comes.)
How would the chainring be worn after 2000 miles riding? And which chainring are you talking about
@derrick ?