The reason the formatting got messed up when you pasted in the code is because you truncated your Dimmer Office_mainlight Item definition. My deleted post was all about that being your problem until I noticed that you have a full and what looks to be correct mqtt config on that Item in your screenshot.
Almost always when the formatting gets messed up in the Forum it is because of a missing or extra ' or ".
Do you have the MQTT Action installed along with the MQTT Binding? There was an error, and since you are running one full release early of a version of OH behind the current that bug almost certainly is there for your, where you may have to uninstall and reinstall the MQTT Action or else the MQTT Binding will not work.
You should be seeing log statements in openhab.log that OH has connected to the Broker when the Binding is working correctly.
Please see MQTT Binding (v1.11) Getting Started 101 for step by step instructions for setting up MQTT and make sure you followed all of those steps.
But to answer your main question, a broken MQTT binding config would not cause problems in your .items files. Only syntax errors in the .items file itself can do that.
You haven’t yet mentioned if you tried ESH Designer. If there is a syntax error it will point directly to it.
There is nothing obviously wrong with your .items file. Perhaps it would be worth while moving the lines over to a new file, one at a time. And retype them, don’t copy and paste. This will eliminate any hidden stray characters that may be hanging about. With what we know right now its a complete mystery.