I pulled out my digital multimeter (RSR 1007) that I hadn't used in a while. It measures the resistance correctly, but the voltage reading is odd (note I've correctly set the range, DC/AC, it has a new battery, etc). For example if I hook it up to a 9v battery, it will take about 5 minutes to slowly drift from 0 to 9v. It seems to measure the voltage more or less correctly, but it takes a really long time, and doesn't seem very accurate, fluctuating more than it used to. I'm just wondering if this is a known/common failure mode, and if so I'd like to understand it and know if I can fix it.
It is capacitor related. Use a screw driver to open the multi-meter's cover and look for any visual capacitor defect. Replace them if you found any. Try to re-solder resistors or any thing that looks loosen and odd.
It is a cheap one, don't waste much time on it. If you can't fix it move on and buy a new one.