Client doesn't give priority in response to a spell with mana dorks that could be activated (Fiery Cannonade)
Basically, title.
Opponent played Fiery Cannode (instant, deal 2 damage to each non-Pirate creature) during my first main phase. I had out two Sanctum Weavers (enchantment creature, tap to add X mana where X is the number of enchantments you control), which would have tapped for a total of 6 mana.
I would have liked to have tapped them in response to the spell - an option which I should well and truly have been able to do, as you can activate mana abilities whenever you have priority. However, the game did not give me priority - I assume because I had no instants or abilities I could use in response.
This is a game-losing issue (lost me this one, and could potentially cause a player to lose a game with actual importance such as prize money). The client has always had issue with not giving each player priority every time they could (notoriously, you have to hold full control when going past your opponent's second main phase if you want to do something before stuff triggers on their end step; if you don't hold full control the game will proceed past their second main phase without giving you a chance to do anything), but this is even worse than that - unless your play every game with full control on, which would be tedious and slow, you run the risk of getting caught by something like this (after all, why would I ever expect a Cannonade in my first main phase when it absolutely should have been cast during my opponent's turn, before I could tap my Weavers for mana?).
Fix your game devs. WotCs getting more than enough money; this isn't good enough.