Have you opened the meter and checked that battery leaked fluid hasn't trailed/crept along and landed on the circuit board?
Check that the internal supercapacitor (cRapashitter) has not leaked or grown a beard
Clean the input terminals, if you see black gunk on your cotton buds, that's resistance you don't need!
Check your leads, clean them too, ensure they 'push' firmly against the input terminal metal,
there is no free ride whether it's a cheap or overpriced multimeter.
FWiW: The Fluke leads supplied with this model meter are a very tight fit (too tight!), with no assurance of good metal to metal contact. Other manufacturers nicer flexible leads with the same Cat specs (
and better HV crosstalk immunity btw) and slightly thinner plastic sheathing work a lot better.
You can tell when their plastic and metal contact connection is 100% when plugging in to the 289.
I suspect a last minute Fluke oversight or corporat nogas on this, that perhaps wasn't considered important enough
to include better fitting leads, rather than their bog standard ones which are ok (but not the best) for all their other meters.
Are they kidding at the price of the meter to not spend 50 cents more on leads, and not subject their loyal customers with athritis and tennis elbow to pushing and pulling hard to remove leads, playing a feverish painful VOA tug o war?
Compare and stress test Benning or APPA meter silicone leads to Fluke ones, and it's obvious the Fluke leads are a 30 yo design anyway.
I still like the Fluke leads, but there are new players on the scene kicking some goals too, and should take note.
Lastly, don't expect a good meter like this that does a LOT to be 100% perfect in everything, it's just not going to happen.
As an all rounder with many bells and whistles
(with the latest up to date firmware) the 289 is hard to beat