I occasionally notice strange behaviour in programs using "tap to select" on my laptop's trackpad (as opposed to "button press to select" with a physical click). If I "tap to select" the playhead on the timeline in the clip transport section, the mouse jumps to the playhead position (as expected) but then behaves as though the left mouse button is held down (ie the playhead position is frozen). This state persists even if I activate other controls (by both tap and click methods). I can double-tap-drag-release to select and move the playhead (without it freezing). Clicking or tap-to-select on the playhead again unfreezes it. As does previewing or launching another clip.
This bug could be hard to squash if your touchpad driver behaves differently. I hazard a guess that you have a state change for the playhead due to a "mouse down" event for which there ends up being no "mouse up" event. Given that I can subsequently click on other controls, I'm guessing each control has it's own mouse state tracking. If that is the case, perhaps you can keep a list (of just one?..) control that has an active mouse state and reset it if some other control gets a new click. Maybe it's a "mouse click" vs "mouse down" vs "mouse dragged" scenario. I'll leave it up to you to do the head scratching!
ASUS R552JK
Windows 10 Pro
ASUS Smart Gesture is installed