Quote form the manual, ent_animate
Quote:

percent : Animation percentage within the scene, 0..100. At 0 the first frame is selected, at 100 the last frame (which is identical with the first for cyclic animation).


It seems that when you turn left, your my.angleturn value is < 0, the manual says that the ent_animate percent range from 0 to 100. Maybe that's the problem. How about using abs(my.angleturn) like:
Code:
...
	if (my._angleturn < 0) { ent_animate(me, "TurnLeft", abs(my._angleturn), ANM_CYCLE); } //turn left -value
	else { ent_animate(me, "TurnRight", my._angleturn, ANM_CYCLE); } //turn right - value
...


or

Code:
...
	if (my._angleturn < 0) { ent_animate(me, "TurnLeft", 100-my._angleturn, ANM_CYCLE); } //turn left -value
	else { ent_animate(me, "TurnRight", my._angleturn, ANM_CYCLE); } //turn right - value
...