The singer and drummer originally hurt himself during the duo's gig in Norwich, England on 18 November (15), prompting Holman and his bandmate Laurie Vincent to postpone a string of shows.
They resumed their U.K. trek in Newcastle on Tuesday (15Dec15), but Holman was soon injured again, dislocating his other shoulder as they opened their concert.
Holman explained the unlucky injury in a post on the band's Facebook page on Wednesday (16Dec15), writing, "I dislocated my other shoulder on stage last night whilst dancing to our intro song (The Vengaboys), I managed to pop it back in after a few seconds and play the gig.
"However I have woken up today and I am in a lot of pain, with limited mobility. I'm off to see a specialist..."
Despite the new health issue, Holman promised to try and play through the pain for that night's show in Birmingham to avoid rescheduling more dates.
"We are still going to try and get through the set tonight, and the following two nights, but please be aware of the situation," he continues. "If we have to cut the set short, or just put on our album and sing along to it or get you lot up on stage and do a talent contest or something, this is why. My joints are not good."
Slaves performed in London on Thursday night (17Dec15) and are set to play their final show of the year in Tunbridge Wells on Friday (18Dec15), before picking up again in January (16).