Do multiple actions work in a single action list if you don't use the extenders?

My recommendation - Don't use PEP3. And if you do, make sure you update the firmware on all your Prontos and Extenders. I see you've updated RFX firmware but did you also update the TSU9400 firmware here?

[Link: files.remotecentral.com]

The simulator does not work by default if extenders are active.

The only way to make it work in the simulator is to used Fixed IP addresses for the extenders (and configure the same in PEP) and install Jon Welfringer's Pronto Simulator Patch.