It's gonna be tricky but you can do it. I'd stop putting new eggs in, of course. The first and easiest thing to do would be to get a second incubator to use as a hatcher, and move each egg into it as it enters lockdown.
The other, trickier method is locking each egg down as lockdown approaches in the same incubator. Just stop turning each egg as it needs it and continue to turn the others. You will need to keep the humidity up for hatching so be sure when you open the incubator for turning that the humidity goes back up after. The other tricky part is that because you will have to keep the humidity high for the hatching eggs, it will be too high for the eggs that are still developing, so you might end up losing some of them, especially the newest ones.
