I get that all the time with my original customs. Thats why I wrote the fancy bleeder into legedit.
Export all the cards without borders first (File -> Export...) on the main window then use Tools -> Bleeder (or whatever I called it) and select fancy bleed as an option. That artificially expands the border so the cut off is a bit less aggressive if they miss align the printer cuts.
Awesome! Super helpful. Although for some reason doing it exactly as you described didn't work for me, but applying the bleed tool to the already bordered pngs worked like a charm! Maybe I should have input different values in the various pop ups to make it work as you described but I just went with the defaults.
Also from the sound of it you are the creator of LegendEdit? In which case you and I have a love hate relationship going on. I love the software and am super impressed with how intuitive it is...but I kinda hate you for making it because it seems to be eating up all my free time.