Idetifying logic icons meaning.

[RolandSol]

Dear friends,

I have a small problem identifying the meaning of the error message that I get in the computer of our mobile crane.
To be precise GROVE GMK 4075. Computer type in this crane is called ECOS.
The error refers directly to the main control box and the only meaning that we were able to decipher from the papers is "One level short" or "One level excess" - look pic attached.
The thing is, we do not know where to look for (as to the error source) because we don't have a clue what the this error may refer to. I suspect that the icons may be some kind of control logic symbols, but after examining several standards I found nothing.
If you have any clue about a more precise meaning of these icons, or about what these phrases "One level short/ecess" can indicate, I would much appreciate your help.
Not sure if its relevant but the error appears after some problems with winching mechanism. (The winch refuses to work).

 

[sfrizzell]

You may have already found the solution, but in case you haven't, and this is just a wild ass guess as I have don't have much experience around cranes, it sounds like the computer is either thinking there are too many cable layers on the winch and / or not enough. Is there a sensor or mechanism that is keeping track of the amount of cable?