Hello,
I have 6330 construction bots. I set the construction bot factor to 1 and "nothing" happened. Occasionally a couple of bots flies away to place something.

Do you have refined concrete available for pickup?

Yes, a half million or so.
I observed, that it start slow and speed up a bit over time. But never uses all bots. Around 1000-2000 max.

I'm getting the same thing on the latest 0.18.x build. I have 10k refined concrete in storage, over 6000 conbots sitting around doing nothing, bot factor to 1, and it rarely places more than 200 concrete per cycle.

Let me spend some time with this and see if I can figure out why.

From what I'm observing, not all roboports are being creeped equally. Some ports are fulling filling out, while others aren't expanding at all. Same network, all powered, plenty of bots and concrete available.

Here's an example: https://i.imgur.com/xpd0dZu.jpg

Note how the roboport in the inside corner has fully concreted, but the ones around it haven't. It seems like something's kicking certain ports out of the "creep here" list for no good reason.

Okay, I've made some changes, should allow for a much larger bot count.