Sag Mill Trip on Ground Fault

Call a service tech.

Hire a competent electrician.

Contact the breaker manufacturer.

There's not much we can do from here, and we don't make service calls.

Get some competent help!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Don't rely on total strangers to trouble shoot the equipment for you.

It looks as though water ingress is close to the top of the list, however, the equipment cannot be seen from here. Follow the good advice in #1↑.

"Severe" ground fault? As opposed to a mild one, or a semi-irritating one? There is no qualitative analysis applicable to a ground fault, you either have one that causes the trip function to activate, or you do not.

Loose connections is a sign of severe neglect (a valid qualitative analysis there). You need a severe professional to do a severe forensic analysis on the cause and come up with a corrective action plan, then devise a preventative maintenance program. These kinds of situations can lead to severe damage, severe injury and severe death if not handled properly. Severely heed response #1.