pressure drop for TDS-11SA , top drive trouble shooting

I will give you some guides to help you, how you will think in this problem: - before we start, we have to decide if the problem happened with function or without function we will consider our problem happened without function. so 1-we can start by PRV "RV1" (adjust or change) (because pressure started by main pump going to "RV1", so if "RV1" had problem, pressure will go direct to tank which cause drop pressure " -----------------------************---------------------- 2-then try "UV1" (adjust or change) the same issue can cause pressure drop -----------------------************---------------------- 3- counterbalance valve, pressure started from main pump stopped at counterbalance valve, if counterbalance valve had any leakage, so pressure will go to tank, and lead to pressure drop. -----------------------************---------------------- 4- main pump also could lead to pressure drop. -----------------------************---------------------- still waiting your ideas, what else we could check to solve pressure drop issue