Quoted from OSUBuckeye98:

Check the switch in the sarcophagus, sounds like it is not registering the ball. At the end of a game my premium will dump any ball still in the sarcophagus and fire it back up from the underworld to drain down to the trough. A lot of people have changed out the stock switch for the rollover switch from pinballlife.

Quoted from ChipScott:

No, this (link attached below) is the micro roller ball switch you need that is exchanged for the current standard micro switches in the trough of the sarcophagus mech.
I used to have the Premium, but now have the Pro. When I did have the Premium, I also exchanged for these micro roller ball switches and all the issues I was experiencing went away after making this change out. I believe there are 2 switches in the sarcophagus mech trough, so you'll need two of these. It's a mini PIA to loosen the mech under the pf and make this change out, but very much doable.
The game was originally designed to have these roller ball switches in the sarcophagus mech, but at the time of production, Stern changed to standard micro switches for some reason.
When these switches are not registering well in the sarcophagus mech, all kinds of funky things can happen during gameplay that are very annoying. This has been reported over the years both in this thread as well as in the "Iron Maiden Issues" thread, which can also be referenced.
https://www.marcospecialties.com/pinball-parts/180-5119-02
Hope this helps.