[GAMEPLAY] Cho-gath can't sell doran ring within Tournament mode

I was playing Cho-gath in tournament mode for Super League Gaming, when I tried to sell the Doran Ring at 40mins, it WOULD let me sell, but automatically buy it again when i try to buy anything else.

For example

1. $3000 dollar initially
2. sell Doran Ring for 160, so $3160
3. click buy for Thornmail (which is $2900)
4. I get DORAN RING
5. BUT
6. $3000

i think it undo my sell of Doran Ring. I tried to buy other things as well, but it just didn't work. I almost lost the game due to this. Please fix. Thank you. I heard it's probably due to the resolution of the screen? I'm using Mac Book Air 13' playing league if this matters.