Add member to group not working randomly

I adding a member into the group and remove it from another group. but it’s working sometimes and sometimes not. some time only remove but not add into another group, sometimes does not remove and add it. it happens randomly. I got success with the null response in every API call. either add to the group and remove to the group.
Any solution?

here is the response i log

here is remove request

here is add to the group request