Pretty much the title. I've had several games are Brand where I'll die, immediately purchase (out of habit), and I believe my DoT ticking counts as a "game influencing action", therefore not permitting me to undo the purchase. It's happened several times.
The reason is quite simple. Items purchased that boost your AP (Ability Power) increase the strength of your DoT ticks. Therefore you could let's say buy Void Staff or Deathcap, get some high damage ticks in and then undo the purchase and buy whatever else. So you'd cheat your DoT damage. Sorry but this sounds intended, not a bug.
The other day someone posted that they couldn't use the redo function at the shop because they went stealth (as Teemo) after purchasing. Just wanted to add that here in case this is a legit bug affected more than just DoT's.
