I'm also experiencing this. most of the time its absolutely no bots buying items, but i've had a Shiv on hard mode be the only one to buy items (opposite team), but got stuck with a limit of 3. I've also seen a Mcginnis (more often than not) be the only one to buy items (up to the maximum) also on the opposite team.
I really hope they fix this issue soon because my friends and I stopped playing from how easy and fast the matches go and how unfair they feel on the other team. We don't play pvp matches cuz of the unfiltered toxicity that valve lets slide so I have been desperate for this to get patched lol