Really? From what I’ve heard, Sir Alec didn’t really want to come back for ESB, and considered using an eye condition he had as an excuse not to resume his role. In the event, some of Obi-Wan’s lines were shifted to Yoda (as both Dale Pollock and JW Rinzler attest), and Guinness ended up filming on ESB for all of one day.
Not an excuse, it was a serious issue and they weren’t sure if he’d be able to film at all.