OP says they are Izuzu 20" wheels ( MUX I assume) and fitted pre-delivery.... Wont be any insurance issues.
The issue will be castor settings... I'd be taking it back to Izuzu, they fitted them !
D-Max
Wheel - 17 x 7 +33 offset
Tyre - 255/65R17
Mu-X
Wheel - 20 x 7.5 +33 offset
Tyre - 265/50R20
Not enough difference between the two tyres to be causing any issue.