Sorry for my late reply. I was aware of the Evil Spirit glitch. This is a problem with versions before v1.3.2. It should be fixed for version 1.3.2 and onward. The version that is linked in the OP is v1.5.0 which should have this bug fixed. A fan recently told me that an earlier version of GJCM (Guy Jepson's Challenge Mode) has been circulating around on a compilation Sega Genesis/Mega Dive ROM hacks. The bug was caused by a code error cause by my initial attempt to make the Creed's Mansion Characters join after beating Zalbard, instead of Frayja joining.
Anyone reading this: Make sure you are playing at least v1.3.2 or later. Any earlier version may be... unplayable.
I would like to issue a formal apology for this inconvenience to any who have been afflicted. I worked hard to make sure my Hack was bug-free, but I must have missed it. I deeply regret this transgression.
On a brighter note, I'm busy polishing up my final version of GLCMv1.6.4 which is, in my opinion, the greatest way to play!