I have an expensive Sumo DT-61 and it is having the same problem especially after i accidentally tested a charged 400 volts capacitor for dc voltage output of an electric mosquito bat/zapper which created a spark onto the lead probe but despite that all other tests are still working except for diode test, continuity test with never ending long beeping sound and ohm mode. My multimeter can accept up to 600 volts max for dc voltage test so I don't know why it is causing this issue. The fuses are also working and I had also changed the battery. I don't know if this is a chinese multimeter but I think that Sumo Industrial is either a british or scottish company based in Glasgow, UK and this multimeter is the most expensive one in the store since it is also an environmental multimeter that can measure noise, temperature, electromagnetic frequency and light. I think that I better RMA it.