The timer for each dealt hand is generally okay, but the problem is that the time posted for the next deal is based on the last deal when the game is returned to Home and exited between games. This gives the effect of adding elapsed time to the next deal.
I just played 20 hands of the event in just over an hour and 20 minutes and then exited to Home and then exited Solitaire. I went to lunch and ran an errand. I came home, started Solitaire and the event and looked at the Leaderboard. My time was still correct. I played my 21st game and it was completed in 2 minutes and 31 seconds. I then looked at the Leaderboard again, and now my time was displayed as over 2 and half hours, affecting my placement on the Leaderboard.
This is clearly a bug and is easily correctable. If it is true that 200,000 or more players participate in each event, then it is unfortunate that Microsoft doesn't address this long-standing issue. Like many players, I am challenged to achieve a high final ranking, but this bug defeats that possibility unless I start the event and plug on with every one of the thirty (sometimes fewer) hands dealt.
It is bush league scoring.