An increase in frequency of behaviour could be due to previous reinforcement of the behaviour, or due to recovery from punishment of the behaviour.
Recovery from punishment; a previously punished behaviour is no longer punished and so the behaviour ‘recovers’, or comes back.
I get to work with horses who have been trained with some fairly powerful punishers (the power of the punisher is dictated by the learner) and often we see previously unseen and unwanted behaviours emerge. These may be the result of recovery from punishment (we are no longer using punishment to change behaviour) or extinction of previously reinforced behaviors (causing resurgence of previously extinguished behaviours).
Often without knowing the full history of the horse (many times this is not available to us) it’s hard to know which it is.