Solution:
EZdrummer responds to aftertouch messages (polypressure as well as channel pressure) by design. This allows you to create custom cymbal ‘chokes’ as required by your track, should the included ‘mutes’ not be adequate.
If you are using an external keyboard controller to program your drum parts, you should ensure that your hardware does not generate aftertouch data. In most cases you should be able to disable this feature in the controller itself (please refer to your owner’s manual for details) but it may require the use of real time filters from within your host application to completely eliminate the issue (details will vary from host to host).
The important part is that this is an EZdrummer feature and not a bug. Aftertouch can be used with great effect to produce custom chokes at the sequencer level (programming), or, with a bit of practice, in real time from a suitable controller (performing).
It is currently not possible to disable aftertouch response from within EZdrummer so should any of the above methods fail to filter the parasitic data you may be required to edit this data post recording within your host application’s sequencer.