Are you sure you are not over filling the expansion tank.
If it's working OK on the lower level then this would seem to be the logical reason for the loss.
I presume it's leaking from the expansion tank, is it passing the push in cap, or how is it escaping?
I would run it at the lower level for a while, keep an eye on the gauge and coolant level and if a dealer can check things over all the better.
And 105 is hot!
Upt.