How to solve Error:DT<DTmin?

When I run the following case, I get the DT<DTmin problem (as shown in the picture), I tried to turn off all chemical reactions and found that the case works, so I suspect that there is a problem with the pyrolysis reaction settings, can you help me with that?
Thank you very much!

biomass pyrolysis-0301.mfx (28.3 KB)
usr_rates.f (4.5 KB)
usr_rates_des.f (4.0 KB)