Veggies might be building up pwatste. Pwaste acts like residue that can't ever be removed that lowers the effective threshold for the bot.
That is, if pwaste + waste > threshold, bad stuff happens ;)
So if pwaste is, say, 200 in a veggy, and it gets 200 waste, it's already at the threshold.
I don't know if pwaste builds up in veggies or no...