Well, it doesn't look like any of the cells dropped below any safe limits. The 3.3v cells are probably the ones that caused the drop / shutoff, and are likely significantly lower capacity and capability than the others, with the next higher voltages being just a bit better off, and so on, till you get to the 3.9/4.0v cells.
The difference in capacity of a cell at 3.3v and at 4v is huge, so my guess based solely on data in this thread so far is this pack is not going to give you anywhere near full capacity anymore (see end of my post for extrapolations*****). As long as you can live with the lower capacity it has at this point, you can still use it, but it is just going to get worse, even after it is rebalanced (because the worse-condition cells probably just don't have nearly as much capacity as the better ones).
Note that a balanced pack simply has all the cells at the same voltage. It doesn't mean they're all equally capable of delivering current or capacity.
So rebalancing a pack that has become unbalanced on it's own only makes them all the same voltage so that they can all charge as full as possible, for whatever each cell can hold at this point. It does not make each cell equally full, equal capacity--that's no longer possible for cells that have become (or started out) as different as these cells probably are.
So, you can put it on charge, then when the charger shuts off the first time, you can recheck balance. It will probably not be much different than it is now. The pack is so unbalanced from the differences in cell condition that it would probably take many days, perhaps weeks, to fully balance just via the BMS, just sitting on the charger continuously, assuming it is even a balancing BMS type.
(Based on extrapolations at the end of the post, there could be as much as a 12Ah difference between high and low voltage groups. Most BMS can do at most about 50mA of balancing current, so 50mAh per hour of correction. 12Ah = 12000mAh, so 12000 / 50 = 240 hours to do that much correction. 24h in a day, so 10 days to rebalance it, typical best case for typical BMS.)
At a guess, it probably is a balancing BMS, given it's size, but some simply aren't, and those that aren't cannot fix a pack with mismatched cells, and can (should) only be used with packs made of well-matched identical-condition cells that are used well-within their limits for current and capacity, preferably never fully charged or discharged and never pushed anywhere near their current-delivery abilities (making less likely for them to become unbalanced).
To rebalance this pack more quickly, you can either drain all the cells down to match the lowest at 3.3v, or charge up each individual manually with a single-cell charger to match the highest at 4v. Either one will require you to be there watching it for the process to ensure nothing gets drained too far, or charged too much, or encounters some other problem.
The BMS, assuming it's a balancing type, will do the job on it's own if left connected to the charger long enough (hours, days, weeks), assuming the BMS has not shutdown input/output due to the huge difference in cell states. If it has, then manual balancing will be required to bring them close enough for the BMS to finish the job. (some BMS will prevent a charge in this situation for safety since cells this far different can be because of a pack failure mode with potential for catatstrophic failure, and it's the BMS's job to protect you from that).
*****Extrapolations (that could be inaccurate, based on insufficient data, actual cell testing required toget real numbers):
Cell link for data, chose that because it was at the top since they don't have the 30Q cell listed and I don't know which they have is closest to it.
https://lygte-info.dk/review/batteries2012/Molicel%20INR18650-P28A%202800mAh%20%28Gray%29%20UK.html
So, this chart shows at different current draws (different color lines) how much capacity a cell has used at any particular voltage (under load, vs your measurements that are with no load, but it gets the idea across). We'll be using the "inverse" of the Ah on the bottom, since it's showing used capacity and we're discussing how much is left.
At 4v and the lowest load (top line) this cell has about 2.3Ah left in it of it's original 2.8Ah. At 3.3v it's a couple hundred mAh or so.
That makes a difference in capacity of this particular cell of around 2Ah per cell at that voltage. 2Ah out of 2.8Ah is about 71% of the total capacity, so there's 70% difference between the best and worst in the pack, based on the above cell data (may be different for your actual cells).
If we extrapolate from your pack's 6P, and using 3Ah capacity found online for the 30Q, your pack could be about 6 x 3 = 18Ah. Assuming your cells are really as different in capacity as they seem based on voltage, then there's 71% x 18Ah = 12.8Ah difference in capacity from the best group to the worst group. Assuming the best group is still 18Ah, then the worst group only holds about 5.2Ah now, making the entire pack only a 5.2Ah pack (at best).
https://lygte-info.dk/pic/Batteries2012/Molicel%20INR18650-P28A%202800mAh%20(Gray)/Molicel%20INR18650-P28A%202800mAh%20(Gray)-Capacity.png
![Molicel%20INR18650-P28A%202800mAh%20(Gray)-Capacity[1].png](https://endless-sphere.com/sphere/data/attachments/187/187334-4487bc7e543476ba7cfc6d8ae359ae60.jpg "Molicel%20INR18650-P28A%202800mAh%20(Gray)-Capacity[1].png")
