What caused problems during grant's presidency apex?

Grant presidency was rocked by series of corruption scandals
 An examination of Grant presidency reveals many scandals and fraudulent activities associated with persons within his administration, including his cabinet, that was in continual transition, divided by the forces of political corruption and reform. Grant problems emanates from factors such as the spoil system.

They made a checks and balance system to equal power within the branches. the "check" meant that one branch would watch one branch and "balance" them if they were too powerful. if you want more info on this, i would just google checks and balance system.