I am no expert on this subject but will relay what was explained to be about replacing the oil. Im my experience (very limited) the 2 systems I had run into with restricted cap tubes was caused from the condensors being blocked and the oil turning to wax. I tried blowing out the tube and was informed on some tricks after I was done working on the machine so i did not try them.
1. you can try and heat up the tube and free that wax build up.
2. cut off the first couple inches of the tube and braze it back in as this is where the restriction most likely occurs ( of course assuming this is what caused your problem..
So, replacing the oil, or compressor ( as it was recommended to me) is a not a bad idea to avoid future problems. Both times Quotes were given for the repairs the customer opted for a new unit..
Like is said ASCJ I asked these questions about 2 refrigerators I worked on and these were the agreed responses I was given. Just wanted to pass this info on to you. Good luck.