Why did my construction workers skip over the 5 medical facilities left in the queue to build 6 light posts?
In order to avoid wasted workers during any given day, the construction queue will skip any leftover items in a queue that they could not complete in a day and will work on whatever they can in following queues. For example, in the question, each medical facility takes 16 workers to complete in a day. So, enough workers were assigned to build all but 5 of the medical facilities in one day with 6 workers left over. Since they can’t build the next medical facility in one day, they go on to the next thing in the queue that they can, in this case lights which only take 1 worker apiece.