The first one is 1 1/2 years old and doesn't click when selecting a function and has begun to read 1/2 a volt off compared to my ~$350.00 Fluke.
Uhh, you did change that crappy "heavy duty" battery, right?
When the voltage readings go goofy, it usually means the battery is low.
I have a $couple true RMS.
Ran a bunch of tests on ECMs (amps, VDC, VAC, Voc...) with the TRMS, a red HF, and a yellow HF.
They were so close that I don't risk the TRMS for silly things.
Usually within <0.1V, worst was 0.2V but I can't figure out why that happened in just the one testing scenario.