The settings in your SmartShunt appear OK which is good as these can often cause an issue. I would however use 4% for the tail current, but that is not the cause of your issue.
The other reason for what you are seeing is the MPPT negative being connected to your battery and bypassing the shunt. If the MPPT negative goes to ground then your ground connection to the battery and common negative to the starter battery also have to be on the system side of the SmartShunt.