The pressure gauge on my Yong Heng compressor started to go south near the end of my last top off. It no longer returns to zero and the needle vibrates quite a bit when it is nearing 4300 psi. I used to think that all of these gauges were glycerin filled to dampen needle vibration. Either my gauge leaked out or it was never glycerin filled to start with. I looked at some Yong Heng compressor ads and some seem to be glycerin filled. What are others seeing on their Yong Heng compressors?