IBT-2 problem

[Evolaco]

Hello,
I have a very strange problem, I used motomonster but I did not get a good result and I bought ibt-2, the problem is that I have a return current of the motors, in the sudden changes the voltage rises, but if you leave the limits of smc3 Turns a turn and I get up to 19V, this causes me to burn 12v fans.
The ibt2 have no protection for this?