OK, so I think I've figured out the issue here... the section below your breakpoint (red line) is supposed to check the filename in the header... check 10 characters (LD B, $0A) and JR to tl_header (JR NZ, $A14B) if any characters don't match.
The highlighted LD A, C should really be LD A, B - however we already know that B=0 after the final DJNZ, making this extra check redundant!
I will test and release an update once I'm confident that this is the issue... it is likely replicated in the main code loader so I'll need to fix there too.
Thank you for efforts and bug report! 🙂