Prep table with 134a. Replaced evap in prep table as well as the pencil drier to an emerson cap-t style. on a return call I found that the cap tube had a restriction in it, so I changed the cap tube and drier and recharged, pressures were 20 psi and 175 psi. Then 3 days later got called back again and found suction 1 psi and hi side at 135 psi, now I believe the cap tube has restriction again. it is most likely the original compressor and I was told to change the old poe oil to new poe. Any ideas or would you agree with changing the oil