I noticed a few threads about this before, with people coming up with fixes that seem really unnecessary, when I got it myself through messing around in the scripts. I didn't want to necro any of those.
Many people have had issues with the Yanfly Victory Aftermath not displaying arrows correctly when using a different or custom font.
I found that simply replacing the arrow in the script still resulted in a broken box appearing, but changing the values slightly fixed it.
Just replace...
Code:
draw_text(dx, dy, 24, line_height, "¨", 1)With this
Code:
draw_text(dx, dy, 22, line_height, "->", 1)