This is what LCI recommends to add to the hydraulic fluid to help eliminate the noise people sometime hear when the jacks are retracting. I did add some to my Magnitude 18 month ago and it did help.
https://www.amazon.com/gp/product/B0...e?ie=UTF8&th=1
I'm took the OP's post to mean he is hearing a noise after the jacks had been retracted. Hopefully he can confirm he is hearing the noise while they are retracting or after they are retracted.