Okay, here is what happening.
Your bots are reproducing through altzheimers. Your waste threshold is set at 400. When a bot's waste level exceeds this, the altzheimers routine writes random stuff to the bot's memory, occasionally hitting .repro or .mrepro and they reproduce.
Bot 344 (lower right quadrant) is positioned right in the sights of a veggy. With the sun off, it's waste level is below 400 but when you turn on the sun, it gets a mouth full of nrg shots, a small percentage of which goes to waste. The threshold is exceeded, altzheimers kicks in and it is the first to reproduce and does so several times over the next few 100 cycles.
This is why turning off the sun appears to stop reproduction and why your bots can reproduce without DNA to do so. It's all about waste as a side effect of absorb ing nrg shots from the veggies.
It's not a bug, its a feature!