swing motor acting up

so on my 270 dlc with 7900 hours on it im having issues with the swing motor not operating properly. when i try to swing it will sometimes not swing for up to 15 seconds and then it will finally go with a bang. other times it works perfect it stops as it should ,it turns properly, everything is perfect. so i changed the swing brake poppet and spring in the pilot control valve cause i figured maybe it is sticky or something but this didnt work. so then i changed the makeup check valves on the swing motor but again no difference. so then i decided to do a swing motor leakage test. i took the small line that goes from the swing motor to the tank return off and stuck it into a jug and started the excavator. my jug filled up pretty fast so i figured maybe the swing brake piston is leaking . so i disconnected the swing brake released line and capped it all off and tried again . my jug filled up at the same rate like a five gallon jug in probably 25 seconds . so first of all while i believe i did do the test correctly i would like somebody to confirm that. i might also note that i hadnt actuated the swing function yet . and if i did do this correctly whats next? thanks in advance everybody