If you set the update DPM and continuous phase source terms to update with every iteration then it is likely to happen. To compute the effect of the heat and mass transfer from the DPM particles to the continuous phase you need to do few more continuous phase iteration before the next DPM iteration. When the number of continuous phase iterations are increased to 10 or 20, the solution should be improved to get the acceptable temperature and velocity values for the particles.

Also please note that the particle diameter should be less than the minimum grid length scale.