Sounds like a lack of engineers. Surely coverage for sick day(s) is possible unless they are running skeleton/sub-skeleton crews. Implies administrative mismanagement of the workforce. Seen that more times than can count.
I think they run really thin. I was reading some posts on another site. They were from these folks about the issue. While I usually think unions “over reach”, some of the stories about their scheduling and turn around times were horrible. It takes years to get a good gig.
But, that’s been true in union shops forever.