Yes, but only for about two minutes, then they were dumped because the protection system was acting up. That's a major PITA when running such machines. The protection system is overly sensitive and needs to be carefully tuned to safely detect "safe" conditions and only report minor deviations. Since it has never been run at that energy with beam it it, there are still a few things to sort out, which needs a bit of time (and a certain amount of trial and error). Well, better safe than sorry.

And, by the way. The beams were stable is not what is meant by the term "stable beams". The latter usually refers to the state when they are actually declared stable by LHC operations. When they are declared stable, the experiments can safely turn on their detectors since LHC then guarantees that no beam will go awry and shoot particles into sensitive parts while they are on high voltage. When LHC declares stable beams, this usually means that they are well measured, well positioned and brought to collisions. The "stable" referred to in the blog just means that they were staying in the LHC and not getting into troublesome resonances and scratching collimators and such. (which is a good thing, since beam optics depend on the beam energy, which means LHC was able to keep things under control while ramping, which by the way they did in an amazing short amount of total ramp attempts, which IIRC you can count on one hand)

Actually, the quenches themselves are not the problem, these are quite under control and during the so-called training campaign something that is even deliberately induced.

The problem here is more a chain of unfortunate events, and something that wasn't expected during design.

Basically what happened is:
- faulty electrical connection caused the power supply to trip (i.e. detect some problem and shut down)
- fast discharge was triggered as a consequence
- during fast discharge the current couldn't be handled by the faulty connection, causing an electrical arc
- the arc burnt a hole into the insulation

This is the first thing that hadn't been considered in the design. The cold mass can withstand a very high helium pressure. Helium is not expected to go in the vacuum outside of the insulation (which is there as a thermal shield).

Then, the next problem:
- the electric arc caused some bad electrical fluctuations, causing the quench protection system in several magnets to think there was a quench
- as a consequence, the quench protection heaters then actually induced real quenches
- as a consequence, a lot of Helium got evaporated, causing the Helium pressure in the cold mass to increase sharply

This wouldn't have been a real problem, hadn't there been the hole caused by the arc.

Now the Helium entered the thermal shield around the cold mass with high pressure, causing emergency shutters installed all 107 meters
to close, which are there to protect the vacuum in the rest of the magnets. Unfortunately they were maximally designed to withstand a pressure of regular atmosphere and not the Helium under high pressure. As a consequence they were completely torn by the pressure, causing connections between magnets to be damaged and even more Helium to be released. Several hundreds of meters of tunnel were affected by this, which leads to my personal conclusion that the pressure must have broken several shutters in both directions, until they could finally hold.

So, as a consequence, the actual faulty electrical connection was a small problem compared to the chain reaction which caused in total 29 magnets to be damaged.

(Disclaimer: Personal interpretation of the incident report, there might be flaws in it)