It only started happening recently? I doubt any of these suggestions will solve anything for you but possibly worth considering if you're looking to try figure it out
-Have you recently added a lot of objects to your object library or planting set? Or possibly a lot of textures? If so, how big is your user.lib file and Object folder? I've no personal experience about this in particular but I know Links (and therefore likely also APCD) otherwise often seems to take issue with very large amounts of files.
-Does it only or mostly happen on certain courses?
-Have you started turning edges often? I suppose this shouldnt be the issue if you get the problem when opening courses...
-If it both happens with or without 2d objects turned on I suppose it shouldnt be those... I think you already know this but 2d objects showing in perspective/game cam is otherwise often a culprit of APCD instability (when significant planting already exist). I limit panning around with 2d objects showing as much as I can and when I still have to do it I change "Object Resolution" to Low when acceptable.
Can also try "Render Hole" instead of "Render Course" when getting through parts where APCD seems particularly unstable.
Edit: also, turn off verts/edges showing when not needing to see them. I recommend using custom hotkeys for toggling them on/off
Hi Sage, just downloaded your last course 
Not making fun of anyone, but it struck me funny this time. 
There is one that fits Microsoft operating systems