Hi guys, I was replacing a M92 and then i realized that many ground points have spikes in readings. For example, in continuity mode, on the ground plane under M92 or even on pin 1 of the usb port i have intermittent beeps, so there’s a resistance to ground on ground points. What it could be the fault? Thanks.
More likely to be your probes/meter, cheap probes are course ground and plated and tyically have high contact resistancee. You can polish the probe tips with > 1000g abrasive paper which will significantly improve your situation. You can even polish them after with abrasive paste (brasso or turtle wax etc) if you wanna go a step further.
Check your leads aren’t the issue, put your meter in continuity, touch probe tips together and rattle the wires about and see if the buzzer is at any point intermittent…
Also, believe it or not, I’ve ran across leads with aluminium core conductors (high resistance) and also leads with incredibly fine copper inside.
Whether your meters continuity mode is latching or non latching could also be playing a part here.
How clean yoyr tips are and also the corresponding pad/point on the board is will also play a part.
It’s highly unlikely to be a board defect.
I think you are right 
I cleaned the probes and it’s stable now. Thanks! 