SkipTransaction after upgrade to 3.8.8

I’m experiencing some problems after upgrading my installation from 3.8.7 to 3.8.8. It seems that my Callbacks are not working anymore. The most important one hides all system transactions as documented here:

The callback is in the same ath as before: /opt/rt3/local/html/Callbacks/MyCallbacks/Ticket/Elements/ShowHistory/SkipTransaction

Unfortunatly it does’nt seem to do anything. All system messages are still visible. Is there a way to troubleshoot/test callbacks ?

Wim Wittesaele