Faulty form fields that only deleting/replacing will fix

I've been working on a project for a couple days. It's not too complex, but has about 20 form fields that are used for either input or calculating a total. For instance, I have one column of 12 fields that are sum totaled, and another field that calculates a percentage of the results. Simple stuff. Only a couple fields have any custom calculation script.

After some time, I noticed that the calculable fields begin to misbehave and no longer properly total or update. Not all of them at once; just kind of randomly, where the sum total will not include one or two of the fields. Or the percentage form is wildly incorrect.

As a workaround, I have been deleting such fields, creating a new field with the same formatting, elements, and name as the former field. Miraculously, the new clone field works fine.

Is this normal? Is it something I'll have to live with? Or, is there a way to prevent this? I'm wondering if the continual testing, changes, and back and forth creates some sort of mess behind the scene.