That is sensible advice, Nigel - thanks. I did check and all the settings look normal (in the normal controls also). I have tested a number of programs and this sticky-click behaviour seems unique to Logic. Also it's not project specific - I checked that. Observing the behaviour in detail, what happens is 1) I click on and release an event in a track 2) the waveform disappears. I can can wait any length of time at this point, the waveform will not return, and it appears while like this I am in "sticky mode" i.e., holding the click 3) If I next move my finger across the track-pad and click in say another track it will drag and drop the event there, and also the waveform redraws. If I was to click a menu item at the top of the screen, it will drop the event into the top most track. Most troubling is making unnoticed small shifts of an event within a track. Suddenly it is out of syc with everything - which is really how I discovered the problem in the first place.
I have just done a complete uninstall-reinstall of LPX, to no avail. At present I keep the Edit History window open and check it constantly to see if I have made any inadvertent event shifts along the timeline and immediately undo them. I also lock any tracks that I'm not editing. Clearly I can't continue to work this way, but I need to finish the current project somehow. This is all for information and I'm not expecting some magic solution. Maybe the next software update will remedy this.
-Terence