Vending Machine Chat Spam

Purchasing from a vending machine will occasionally result in the message "You're not authorized to administrate this vending machine."

This typically happens to me with multiple purchases in a row (happens at least once or twice per 1-2 vends).

Additional info: I type in the number of items I want to buy in the number box (spam 9 until vending machine defaults to max number), select 'vend', then every one to two vends this message ends up in my chat.
I have not had this message pop up when just selecting 'vend' (not changing the value), or by using the '+' button to increase the value. It is only when I type in 9's to get to the vend cap as far as I can tell.

Not a huge problem, just a nuisance to have only this message in my chat sometimes.