I added 2 additional System Parameters to an Event Handler.
I then transported the changes to QA.
When I ran /saptrx/eh_list I could see the System Parameters were added.
However, when I tried starting the Web Dynpro (/saptrx/em_start) I got a dump.
After 5 hours the Web Dynpro mysteriously started working again!!
My best guess is that the System Parameters were updating the back-end database.
I've noticed the same thing happen every time System Parameters are transported.
I tried running /saptrx/ucpd_delete_obsolete_f and /saptrx/upcd_create but they had no effect.