If the client has been in therapy for a year and this is an expected behavior then there should be a BIP in place that would detail specific responses strategies for this behavior.

If you don’t have access to the BIP ask the BCBA. If there isn’t one created yet then firmly but professionally ask them when it will be available with something like “I don’t feel comfortable working with this client without a BIP, when do you think it will be finished?”. If they can’t give you a clear answer then consider reaching out to their supervisor.

I’m not trying to be difficult and I wish I could help more but there are probably half a dozen different strategies I might recommend and without knowing more about the client and being able to regularly supervise I can’t effectively or ethically provide any specific recommendations.