Degeneration of Macbook Pro trackpad performacne / janky cursor movement

I have Macbook Pro 2009 model. I have been travelling with it in tropics and slowly trackpad performance has gotten worse and worse, to the point it is almost unusable.

The symptoms

• Mouse pointer movement gets "janky" and it jumps around, not responding to movemements smoothly

• The trackpad works ok after reboot, even if it was totally unusuable few seconds ago before the reboot, so the software must play its part in this issue

I suspect some kind of calibration issue related to humidy. Maybe trackpad recalibrates itself on every boot, but somehow gets slowly off sync from the calibration during usage?

Any ideas how to further debug the issues? Hardware failure?

Each user account has its own trackpad settings.

You can easily figure out if it's a hardware issue or one of your System Preference settings by making a new user: System Preferences/ Users and Groups / hit + for new user.

Log out of your current user account and log into the new (clean) user.

If that helped log out and back into your user account and check any of the settings that can affect trackpad input, including Universal Access.

It's a long shot, but have your tried to turn off your "accidental trackpad input"?