Question regarding enhancement scrolls

Hypothetically speaking if I had a +8 190 atk weapon with 2 failed slots and I used an enhancement scroll on the weapon bringing it to 194 atk, would the +4 automatically turn into a +5 if I clean-slated the 2 failed slots and scrolled the weapon to 200 atk?

If you successfully scroll the last two slots to 204att, then yes, you would start gaining +5att when using Enhancement Scrolls.