I’ve found the solution, you should put seed before train phase. So, it will looks like:
init model
     v
K-fold CV with 60% data A
     v
Validate with 20% data B 
     v
Seed model again
     v
Train with 80% data A+B 
     v
Test with 20% data C

I think it happens because dropout randomize run every fold but seed only run in the first time of initiation