https://www.theverge.com/2018/8/9/17671558/microsoft-surface-pro-surface-pen-firmware-update-accuracy-issues

Microsoft is addressing Surface Pen accuracy issues with its latest Surface Pro tablet. Hundreds of Surface Pro owners have been complaining about Surface Pen problems with the device for months, noting that the Surface Pen becomes inaccurate when you rest your hand on the Surface Pro screen. Microsoft has been investigating a fix, and the latest Surface Pro firmware update (available on Windows Update) now addresses problems with palm rejection affecting Surface Pen accuracy.

Affected users have confirmed pen strokes are now fully accurate when resting a hand on the Surface Pro screen. Microsoft’s latest Surface Pro isn’t the only device to experience strange screen-related issues in the Surface lineup. Earlier this year Microsoft launched a warranty replacement program for Surface Pro 4 units affected by screen flickering issues.