Sheridan Sheridan blue streak pumping issues

Just got a blue streak that’s having an issue pumping. It is holding air but has a whining noise and occasionally after 2-3 pumps the pump arm almost seems to feel stuck in the open position and have to force it closed. It seems to be shooting quite well but don’t want to damage any further. Assuming it’s something with the pump assembly and hoping someone can point me in the right direction to fix it.