Thank you for your post. I have been able to reproduce this issue again (I thought I had fixed it!). I am currently preparing a new version which I will post here for you to test.
You can download the new version from here: http://downloads.playitsoftware.com/Live/PlayItLiveSetup_184.108.40.2068.exe
Uisng latest version of Play It Live (1.14) . Am using Windows 10 PC. Can start stop and pause tracks in Decks mode but not in Live Assist mode except by 'ejecting ' track. Keyboard shortcut seems not to work either. Am I missing something or is there a bug?