I cast a brain freeze with 2 storm, so I had 3 copies targeting my opponent. My opponent then cast a mystic confluence, with each mode targeting a different brain freeze(so each of the 2 copies and the original were countered unless I pay 3). I used LED, lotus and lands to pay 9 mana to prevent all 3 from being countered, but both of the copies were countered anyways, although the original resolved properly anyways.
The attachments are from an untapped replay, since I didn't notice the bug as it happened. The first screenshot shows the confluence targeting the freezes, then you can see two copies were countered and only the original remained at the end even when used the mana, while they should resolve as normal since I paid mana(I used autotapper to pay, so you can see the lands tapped at the end.)
I play on windows steam version.