This is not a near-term concern. If FRB was concerned about capital levels, they would have required it prior to allowing the deferred interest to be paid. Only reason that interest won't be paid going forward is if they run into some new financial trouble.
In situations like this, they usually don't go straight to full value on the first day. I expect it will continue to inch higher over time, but may not trade close to par until after the interest is paid out. One reason that people might be selling is because today will be the highest volume day in the recent past or future, so if you own a lot you might prefer the liquidity and the certainty of today's price over less liquidity and a potentially higher price later on. I personally have no interest in selling at $34.