On PTR4, I switched from Rhinos to Moles, and so decided to tidy out old useless schedule Sets.
First save a newSchedule set for the moles (mix2_lvl3) - possibly was overwrite of an existing one. Then go to loadSchedule set.
The list shows 3 entries - the wrong ones are greyed out [also, unless those two sets are identical, how can I currently be running both of those: I guess could be identical rhino schedule sets.]
Normal condition now recovered - I created a new schedule set, then overwrote mix2_lvl3, resulting in mole_load_ok.png
Not sure how to reproduce.