I had this happen to me multiple times with my Abu Garcia's. One day it didn't work and then the next it was fine... weirdest thing ever. I even had it happen to me right after having the reels cleaned. That's why I switched to Shimano. I was tired of having problems with my Abu's. Haven't had the problem since I switched to Shimano. I don't like bashing other brands but the quality is lacking in some of the high dollar Abu's.
I have a Steez with that "gremlin" right now. Turns out the neodymium magnet ring is poorly glued into place and the polarization of the magnetic force changes as I turn the dial. "0" is all braking force. if I change it to "5", its normal for a few casts...then "5" is maximum braking force...move to "10" ...and ....well....you get it. Back to "0".....and again. You get it.
I have to send that one back for service as I have no idea what is the proper radial position of the ring magnet is in relation to its retainer. It also happened after I cleaned it with rubbing alcohol. I probably soaked the glue with the stuff and released the glues hold on it.
You might check for something similar if it has magnetic brakes. You might check for sticking "clickers" if it has centrifugal brakes.