That's normal. Set $DMAURST (deadman auto-reset) to true if you want the fault to reset when you pull in the deadman instead of requiring a push of the "reset" button.
This is only working for controllers with software version older than V9.40. Since software version V9.40 there is a new DCS parameter called "TP Enabling Dev Reset" which secures the $DMAURST variable.
When changing TP Enabling Dev Reset to ENABLE then $DMAURST automatically also changes to TRUE.
If the parameter is set to TRUE it is only possible to automatically reset the "Deadman released" alarm. Other alarms reuire to push the reset button.