I also had this issue just now. Got taken to sideboarding as though it was a brawl game in Traditional Standard Ranked.
Stopped playing for a couple of weeks because of so much frustration due to this issue, decided to come back because I watch magic youtubers and they make it look fun, instantly reminded of why I left every single game for the first three I played and then at least once in every five afterwards.
It's been 4 months and at least that many updates now since this issue got posted and still no remotely useful comments or timeline or anything from Wizards on this issue. Please give us some indication that you care and might be even in the earliest stages of looking into resolving this issue.
Wizards support staff commenting on this thread could you stop redirecting people to log this issue under different sections. By this point it is very clearly an issue on your side, even streamers are showing the issue in YouTube videos, let alone what goes out live on Twitch.
I was hoping that this would get fixed with the full release of the game from beta stage since its been an issue for two months now, but no such luck. Would very much appreciate not having to force close the client every third game because of this.
I have had this problem multiple times in Traditional Ranked and Play 2020 queues recently.
@Wizards_MS14#29616 thanks for letting the op know where to post for an event-specific issue but as you can see from the comments on this thread from various users, it's clearly an issue in multiple events.
Edit 16/09/19: This has just happened again today.
Would like to comment that this bug is still happening despite at least three client updates since this issue was posted.
@Wizards I've noticed from the game freezing during sideboarding that the timer didn't progress (skip forward) as I would expect it to given the extra time since the last frame. Therefore I think this could be connected with the other bug where the game freezes before sideboarding, causing the actual timer to start before sideboarding and the orange fuse begin on our screens.
If this is the case then connecting the orange fuse progression to the actual timer would solve it as the above indicates it just progresses a bit more each frame or something like that.
This has happened to me many times now and I'm tired of loosing games because of it.
If there is some other timer going on based on whether you are interacting with your deck that's cutting it short WE NEED TO KNOW ABOUT IT. Put it on the screen so we can see how long we actually have. Is having two timers on the screen at once too much for us? DON'T HAVE TWO TIMERS.
This is not a small issue, Bo3 is fun because you get to use a sideboard. What cards you put there and which ones to use in certain matchups are some of the toughest decisions to make in the whole game. My understanding is that Arena's goal is to attract new people to MTG and test out decks. A two-minute timer is fine, but we should be able to think about our sideboarding without worrying that our deck could be re-submitted without any changes at any point.
Absolute minimum: tell us how the timer system actually works.
Expected: make a simple two-minute timer that actually works with no fancy bits.