If there are any residual voltages on the circuit board that appear across the component being tested, this will upset the meter reading. This can happen because of charged capacitors. For instance, if the ohm meter's open-circuit voltage is (say) 1 volt and you try and measure the resistance of a 10 kΩ resistor that has a residual voltage of 1 volt across it, then the meter will read infinite ohms because no current can flow.
And, if you reversed the probes the meter might read a negative resistance. Be careful about measuring resistances on PCBAs that still have charge remaining on capacitors. Here's a situation that would show exactly 0 Ω even though a physical 10 Ω resistor is supposedly being measured: -
simulate this circuit – Schematic created using CircuitLab
So, if you want to measure R1 above, first try measuring voltage, and see that 0 volts is indicated. Anything else would is a red-light warning if you then tried to measure resistance.