I can recreate this everytime:
Create a new property/value. cursor: pointer; for example.
If I toggle the rule on and off LiveStyle updates the css in Sublimetext just fine.
If I, however, use the keyboard or mouse to delete the property/value and then recreate them I get the following results:
An extra semicolon at the end. If I repeat several times, more semicolons appear:
Windows 10 - Sublimetext build 3126