However, if you try build another blueprint (just say you restricted that supply of concrete to free up some robots), there will be no movement for a minute or two, before everything then kicks into action. All the construction robots are marked as 'available' and it's pretty confusing as to why nothing is happening.
I know it'll be something to do with the optimisation in a way that you won't notice most of the time, but the delay becomes very obvious when 99% of the jobs are all 'missing item' ones. I think newer blueprints should get priority anyway (maybe find the nearest robot not carrying anything and reassign them for each item), which would possibly also solve this problem

I can attach the save if needed, but I'm guessing it's a general thing.