[BUG] JMXclient does not work

[dizzzz]

When starting the JMXclient, a number of issues appear:

1. due to missing values in an array there are array-out-of-bound exceptions
2. a bit deeper some data sources do not seem to be there or are maybe renamed. Need to check Monex here.

it has nothing to do with #5706 though there are some linked PRs in an offside solo project.