The key shortcuts are case sensitive. you can’t press Shift-P or CapsLock-P to play the video in a tab. You can only press P to do so.
The keys that are affected are P, 0-7, and H, J, K, L, and ;.
When you press Shift on P and 0-7, nothing happens, but the plus indicator for joining note lengths activates. The note length keys works as normal.
When you CapsLock is turned on, P does not function, and the note length keys have this odd behavior where it acts like Shift is being pressed until CapsLock is turned off. 0-7 works as normal.
I can confirm that this bug still exists in the flash version (specifically Hookpad 1 for Theorytab).
In Hookpad 2 (HTML5), when caps lock is on, the note length keys specifically (H, J, K, L, ;, and ') don’t behave as they should. Pressing Shift to join different note lengths does not work when caps lock is turned on.