I was just using the PLC-mon screen to solve my I/O board problems for my oil pump. I don't know if your machine and mine use the same I/O boards, but your PLC-mon screen should show all inputs and outputs. For example, outputs 1-32 (board 1) and 1-32 (board 2) represents the outputs on the X2 connectors on the #1 and #2 I/O boards on my machine (a Maho MH1200C).
If your machine is like mine (which is very possible), I think what you are seeing is input X4.22 on I/O board 1, which comes from the Main Drive Load Indicator, an opto-isolated module that I believe shows the load on the main spindle. So, yes, input 22 (as well as inputs 20, 21, 23 and 24) would change due to running the spindle. But, I don't know what is normal. This appears to be a 5 bit A to D sensor.
Some info on the PLC-mon screen and I/O boards.... (You'll have to check your machine schematic to decipher things for sure.)
My machine has two I/O boards, 19A1.3 in slot 3 is I/O Board 1, and 19A1.2 in slot 2 is I/O Board 2. On both boards, connector X2, a 37 pin DB37, drives the board's outputs, and connectors X3 and X4 (DB25) are the inputs. The I/O number on the PLC mon screen matches the pin number on the connector. E.g. Output pin 22 is output 22 for that board on the PLC-mon screen. Pins 33-37 on the DB37 are not used. For inputs, I'm not sure how the numbering matches, but it is probably pretty obvious if you compare to the schematic, or look for an input you can monitor and see compare to your PLC-mon screen.
On my PLC-mon screen, the right half is I/O board 1, and the left half is I/O board 2. It's a very useful screen, but there's no documentation about this screen in my manuals. I had to figure all this out by comparing to my schematic, and checking real wires with a mulit-meter to see if their signal matched the PLC-mon screen. After a few comparisons, it all made sense.
As for why your KDA drive isn't working... What error codes are showing up on the 432 screen? If there isn't an error code, I don't know what to suggest, but these machines trace just about everything that can possibly fail. There should be an error code. Trace those errors, and you might find out it isn't the drive at all. The machine might be shutting down the drive due to an error condition somewhere else on the machine. That oscillating input 22 might be a clue. Maybe it's a failure with the spindle load sensor, and the KDA drive is being shut down because of it.