I have the same problem.
How about this one.
Cutting in the timeline, match frame to a source clip to find another shot, Apple+3 or click on the timeline to reactivate the timeline, when you hit spacebar, the source shot plays. Click on the timeline again, the source shot plays, and over again. Until I click on the timeline a few times to get it to activate.
Might be a related issue.
HSY
http://www.hspenceryoung.com