Hardline is 100% on the money with the suggestion of getting a qualified (JLG certified) technician to give this a go-over. Records of inspections and work performed on this machine would be helpful as well.
Who wrote that "Boom Encoder needs to be repaired"? A certified technician or some schmuck trying to unload the machine and had to write something that sounded good but hard to verify?
There are a few sensors and circuit boards used to maintain a safety envelope for the machines safe operation.
It is imperative they function properly or the machine WILL tip over.
Again, as Hardline pointed out, a boom length indicator, the Load Management assembly and also a pendulum angle sensor for boom angle monitoring. These sensors communicate with circuit boards located in the Lower Control Box.
These cards are adjustable but ONLY by JLG certified technicians. These are VERY crucial adjustments for the stability of the machine and the life of the operator.
Any attempt to just cobble circuits together or bypass any safety circuit to "just get the thing going" will put the operators life in great danger and also risk the safety and life of other bystanders.
When these things tip over they make one hell of a bloody, painfull and expensive mess.
Having said all that:
Here are the links to the JLG 110HX Service and Parts Manuals if you don't already have them.
Read and understand before making any attempts to operate or diagnose.
Please be Safe
https://csapps.jlg.com/OnlineManual...0HX/Service_3120636_03-11-10_ANSI_English.pdf
https://csapps.jlg.com/OnlineManual..._110HX/Parts_3120637_7-29-11_ANSI_English.pdf