Error dt<dt_min MFIX-DEM

Hello, everyone!
When I run the mfix-DEM, I met the following problem.

Fatal error DT < DT_MIN. Recovery not possible!

I tried reducing the DT_MIN setting, but it can not make the task converge.
These are the related documents, thanks!
L.zip (1.7 MB)

After that I tried to increase bc_v_s, but the error became

Error 1100: Unphysical gas phase volume fraction calculated.

These are the related documents, thanks!
LTRY-ERROR.zip (6.4 MB)

Thanks for your help! Any input is appreciated!
Thanks,
My