Two tnt carts exploding when turning?

*What I expected was the carts would collide and turn back around like all other carts

*What actually happened was the carts got to the end of the powered rails and blew up..

2 powered rail tracks 9 blocks long with 3 blocks in between them powered at same time at one end and connected at the other end with regular rails so in the shape of the letter U

there was no activators used...

THEY DON'T COLLOID I TRIED RUNNING TO MINE CARTS AT EACH OTHER AND THEY DON'T BLOW UP! ITS THE TURN THAT'S THE ISSUE THIS IS NOT A DUPLICATE!