12v charge line fuse blown from tow vehicle

the few times I have checked the 30 amp fuse that protects the 12 volt charge line running from the tow vehicle to the trailer, it has always been blown. So it makes me wonder why that’s happening. Must be from running the jacks down while the umbilical is still connected maybe? I’m mean unless you’re occasionally checking trailer battery voltage while connected to a running truck, you really wouldn’t know would you?
It’s making me rethink keeping the truck hooked up while running any large electrical loads such as the landing gear or slides.
Wondering if anyone else has ran across this issue or let me know what I may be doing wrong thanks.