problem with world machine tiles build loop

i have a very huge issue with world machine, when i try to build tiles in world machine, when the building reach the 75% of progress it return to 65% and i don’t know why.
but 1 of 16 terrain that i building is built in 4845 seconds and the others it still continue (29644 seconds).
i have 16gb ram, i7 6700k.