smooth brush doesn't work properly on high res

smooth brush doesn’t work properly on high res model. it smoothes out very slow with lot of oversmoothing it. I think it’s some kind of bug because i have sculpted other model in past and smooth brush worked normally until now.
can you give me some advise how to deal with bugs and how to remove it? will deleting blender and installing again work so i can keep working on my model that im stuck in?

multires or dyntopo or none of them ?
high res, you mean what kind of polycount ?

I always noticed the smooth brush in multires working very slow and very weakly when in multires at high polycount, not sure if it’s what you mean, while in dyntopo at high poly i never had such a problem