Also noticed the fill plug looks to be stripped out. Did you replace it with a new one?
That happened to the front of my unit as well as I stripped mine out the very first time trying to check the fluid at 30~ish hours (yes I was using the 8mm Allen). At first I thought the hulk at the factory simply over tightened it. Spoke to a new local Polaris dealer that moved into town a year later (not the dealer I purchased the machine from) and they of course were no help and just wanted to charge $$ to "fix" it to get me to go away. I got mad and walked out and went back home. Got out the cold chisel set and beat on the outside edge to break it free (this way no heat was involved). Then faced it with the flapper wheel and welded on a 3/4" nut and painted it silver. Done.
It is then I realized why the units strip out so easily: it is soft steel to begin with but more importantly, the machine that makes these units leaves behind the "shavings" inside when the hex is punched which prevents the 8mm Allen from being inserted all the way. So, a stripped out front diff fill plug is almost inevitable! Everyone like pics:
Funny, I then checked the front drain plug, rear drain plug and rear fill plug for which none of those had the metal shavings left inside of them! They all broke free with no problem. The oil in the above pic is because the factory did have my front case slightly overfilled (imagine that).