I am experiencing erratic behavior of my Macbook Pro (2020) trackpad. I can't seem to be able to precisely target anything, with the mouse constantly jumping around during movement (sometimes jumping small distances like jittering, sometimes large distances).

I used FingerMgmt to capture the actual inputs received from the touchpad. What I see is puzzling:

Trackpad jitter in FingerMgmt

I tried restarting the device, but the problem persists.

1 Answer 1


Upon unplugging the Apple Macbook charger the issues disappeared! I happened to be charging the Macbook on a train (ICE 3 in Germany) when I experienced this issue.

Further experimentation points to an issue with grounding/static charge/electric potential: When I simultaneously touch the metal macbook casing with my palm while the charger is plugged into the train, the trackpad works as expected. I guess there might be a mismatch between the potential of the train car (and in extension, me) and the internal electronics of the Macbook which are connected to the train socket, causing a current flow through the trackpad which messes up the touch detection.

  • 1
    Out of curiosity, what further experimentation did you carry out to reach this conclusion?
    – 2br-2b
    Commented Apr 29, 2022 at 12:20
  • 2
    Macbook unplugged -> no issues. Macbook plugged in, not touching case -> issues. Macbook plugged in, touching case with the palm of the hand using the trackpad -> almost no issues. Macbook plugged in, holding it in one hand, using the trackpad with the other -> almost no issues. That's all, unfortunately I don't have a multimeter with me :D
    – ApolloLV
    Commented Apr 29, 2022 at 12:51
  • same here as @ApolloLV points out
    – Ev0oD
    Commented Aug 30, 2023 at 16:39
  • Similar, here. Irregular mouse motion exactly while not simultaneously touching the case. With or without charging cable, no difference. 2019 MBP. Misbehavior started quite suddenly, over a day or two, after 3+ years of no problems, hardly ever moved from my desk. Commented Dec 6, 2023 at 18:12

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