Before you uninstall and reinstall...
On the "units" setting page, what is the "precision" for your hops units? What you are describing would exactly describe a situation where the precision is set to "0". It should be "2" for most people. BS2 will round to the number of decimal places in the precision field. If your increment were set to 0.25 then the hop would be incremented by 0.25 each time, but the displayed value would be rounded (up or down accordingly). Once the increment crossed the 0.5 threshold it would be rounded up to the next display value.
Eg.
add 1.0 oz of hops
increment button, internal value changes to 1.25, but displayed value is rounded to 1.0
increment button, internal value changes to 1.50, but displayed value is rounded to 2.0
increment button, internal value changes to 1.75, but displayed value is rounded to 2.0
increment button, internal value changes to 2.00, but displayed value is rounded to 2.0
increment button, internal value changes to 2.25, but displayed value is rounded to 2.0
increment button, internal value changes to 2.50, but displayed value is rounded to 3.0
Note how many clicks it takes to go from 2.0 to 3.0 displayed ounces.