It could be crap stuck to one of your ABS sensors/reluctor rings, best bet is to clean them all up and see how you get on. If the problem persists with your cluster, id advise getting the fault codes checked because if it is actually an ABS fault, the faulty component will be identified, and if it is a cluster fault then there will be an 'internal hybrid instrument cluster failure' code in there. Although it doesnt sound too much like a cluster fault, as the ones ive looked at have all had intermittent speedos and tachos (dropping off to 0 when your driving, then shooting back up) with random lights flickering on and off etc. I think ford dealers replace these for £99 or £129 all inc if this is the fault.