Board Thread:Questions and Answers/@comment-45876740-20200523042748/@comment-27713488-20200607021204

Okay, earliest save is the Erosian Temple near the end of chapter 4, so all we know is that it happened sometime before that. Not very helpful. Why do you only have 10 saves for a whole run...?

There are only 4 points in the game when Robin becomes unremovable. 3 are in the Order trials and 1 is in the Erosian invasion of Arclent, which you mention in your OP. However, all of these are followed up with events that reverse Robin's unremovable status, and I don't see any way for a player to avoid those.

Best guess is that you played the Erosian bit months ago, when there was some bug that has since been fixed.

The most I can do for you is fix your save. https://gofile.io/d/VFBUhE