Alright, then you were probably just not making firm contact on one or both terminals with your probes, causing an error with your reading.
You have now had multiple issues with properly using your meter. In resistance checks, you have the built in safety of not testing live voltages. Your next step will not have that safety net.
In your case, I absolutely cannot recommend proceeding with your voltage checks unless you are using a clip lead on your ground connection. You should also not do the test unless you have someone else there in case you get into trouble.
