[GAMEPLAY] ARAM, can't undo bought items while dead

The champion i was currently using was Teemo (with the Beemo skin, ladybug chroma). Everytime i died and bought items while dead, i was unable to undo bought items. However, if i re-spawned(currently alive after i died) and bought items, i was able to undo bought items. To be honest I don't know what may have occurred or it is a feature in ARAM but usually on Summoner rift, you're able to undo bought items even if you're dead. I noticed this bug at first when i first died and bought boots and 1 potion , i wanted to undo the bought potion. I noticed this happening again when I bought my . These occured while I was dead and I was unable to undo these already bought items. Also, the button to allow me to undo didn't highlight even after I respawned while i bought these items when i died.