Same thing happened to me, reset to the save just before the event and tried again but the Save button still disappeared. Tried flying to different towns, going to different areas with a scene transition and sleeping at home incase any of those counted as new areas or time advancement but it didn't work.
Anyways,
SINtax EroRR is it hard to assign like HM functions to different moves? Just asking cause since there's now a new waifumon that has wings you don't really need a bird HM slave to fly around, but it's also a shame to teach Drakaiden Fly. If it's easy to implement maybe you could attach it to Dragons Descent.
Like I assume the rocks that Gardevoir flings away, Rock Smash, are just events/switches that if she's in your party they disappear so that's probably easy enough compared to what I'm talking about. IDK anything about Pokemon Essentials and maybe you already made it complicated enough by making it a dual-type attack but just my suggestion.