Fork Noise Showa Forks

sounds like the inner chamber seal blew and lost some of the inner chamber oil , Now ya have a vacum in there.

The seal on the bottom of the cartridge was most likely damaged when the forks were worked on last. The thread at the bottom of the damper rod is like a razor when you run your finger across it. If the midvalve was reworked and the service guy pulled the threaded portion through the seal (as he would have too to change the mid valve) without first addressing this, the seal will have been damaged, the oil will escape into the rest of the fork and your cartridge now has air in it.
If your midvalve has had work done on it, I would take the fork back and have them replace the seal.
But they need to beaware that the same thing will happen if they do not firstly smooth of the sharp edge thread and pack it with grease before running the threaded portion through the seal. You might want to check the other side too.