Hi
1-How much is frequency of your PWM ?
2- why you didn't use eliminator filter in your out put terminals ?
3- why you've connected D1 and D2 across the mosfets ? your mosfets have internally diodes hence those diodes are not required .
4- see the voltage across the GS of each mosfet . and show me the results .
5- see the voltage across the motor and show me it .
6- see the voltage across the DS of each mosfet and show them .
By the way decrease the series resistor with gates from 330 ohms till 10 or 4.7 ohms .
7- Be sure that you don't have over lapp problem .
Best Wishes
Goldsmith