It sounds like too high AOA yes.
But it is a standard wing and board, that should work together, right ?
So seems like an error, IF it is very wrong in angle of attack (angle between front wing and tail stabilizer).
Both the straps and wings should be set to work, if delivered as a "unit" - so quite odd if it doesnt work ?
Hawaiis is right also, that going from a low ar easy wing to a high ar race, is really difficult in terms of pitch control, and many says it is like you have to learn everything from start again, when changing
But it must be set up wrongly, as you say it will pop up itself, no matter what you do with front foot pressure, even when moved to the most forward position.
Then something is wrong, indeed
Have you asked the manufacturer ?