MPU-6050 Product revision errors

If I stop and restart the DMP using the UMPL, I consistenlty get an "Unsupported product key" error. However, this does not happen when I first start the DMP. Any ideas what could be causing this?

Here is a log:

// Initially, everything is fine...

V/umpl-states:UMPL_STOP to UMPL_RUN

I/mldl_cfg::Reset MPU6050 B1

V/MPL-acc:THS: 80

V/MPL-acc:THS: 40

V/MPL-acc:DUR: 1000

V/MPL-acc:DUR: 2540

..

..

...

// After calling umpl_stop() and umplStartMPU()...

V/umpl-states:UMPL_STOP to UMPL_RUN

I/mldl_cfg::Reset MPU6050 B1

E/mldl_cfg::Unsupported product key 400 in MPL

E/:..srcumpl2litemldl_cfg.c|inv_mpu_open|2275 returning 19

E/:..srcumpl2litemldl.c|inv_dl_open|195 returning 19

E/:..srcumpl2litemldmp.c|inv_dmp_open|93 returning 19

E/:umplStartMPU Error 19