Hi Eric. Glad to hear you're liking the new Concert Band Combo in VDL 2.5.2!
My first hunch is that your sustain controller may be activated. Have you used any pedal markings in this staff that may be unresolved? Even if not, I wonder if there's some text somewhere that's causing the sustain controller to be activated.
The sustain pedal is controller #64. So try typing [i][b]~C64,1[/b][/i] into the staff (prior to the phrase you're having the tambourine problem) and see if that fixes it.