Awful Shift Work

Are all his colleagues working a similar shift? No point going to a manager on his own. He would need to go as part of a unit. Is he in a union by any chance?

As speak now posted, I'm also reading that your husband is working a four cycle shift pattern. I spent the best part of 15 years working 4 cycle, it's taken it's toll on me, I gave up shift work about 5 years ago, and am still not fully recovered. There are a couple of variations of 4 cycle, but they're all poor. Other shift patterns never bothered me, but 4 cycle is uniquely bad, it's the quick turnaround from nights to day shifts that were the hardest aspect.

A large number of Pharma companies and the likes of Intel all work 4 cycle (IIRC). The 33% shift rate can be enticing, but it's not worth it. I would suggest your husband start applying to companies, or inquiring on the like of Linkedin as to what the shift pattern is at a given company. Being five years out of manufacturing I'm not overly familiar on what companies are not working 4 cycle.

There is a lot of demand for Maintenance / fitters out there, outside of the manufacturing industry. Facilites is one industry, there is demand for the likes of Fabric Techs/Maintenance., the money can be decent, but won't compare to a high end manufacturing job, especially with the shift pattern in mind, the hours are good though, rarely shift based. I've spent time in the Facilites industry, the soft services side can be nonsensical at times, but the hard services side can be interesting, hard services being maintenance and such, it's really not a difficult job.