Simulation converging error

Dear Expert,
I am solving a 2D TFM case, using wall BC (specularity coefficient) and viscous stress model, and using a custom drag model, but when I run this, the following error comes DT < DT_MIN. Recovery is not possible! I think the simulation is not converging.
I checked my geometry meshing, BC, and Numerical value, material properties but the error is the same. could you tell me how I can solve it?
I want to use the specularity coefficient for calculating the effect of wall and particle contact. How can I modify this in the simulation? (58.1 MB)

Dear @jeff.dietiker
Could you pls suggest to me what I am doing wrong and why DT < DT_MIN. R error is coming