I don't know if the dive was still able to use the MAV of the sidewinder, but remember it is an mCCR. So you have to add oxygen manually. If there is stress, the orifice can provide too less oxygent and then you will need the mav.
I don't know if this was a reason to bo or not. But to bo you have to be able to catch the regulators of your bo cylinders. In a very narrow cave, this can be hard too. Especially if the viz is also zero.
So is this restriction so long and narrow that there is a chance you cannot reach things anymore?
6 or 7 years ago I did a solo diving in a cave with a very small entrance. It was my first dive in that cave, and people said, you only have to push the left tank in front of you. So I did. As soon as I was 3 meter under water, the viz turned into zero and I was able to attach my reel from surface to the mainline. But I was also stucked due to the right cylinder. Happely I did not attach the richt cylinder at the back, I only had the valve under the bungee. While I was trying to get in, my mainlight went out. So I must have hit the offbutton/handle of my cannister with the gravel or something. I was in complete darkness. Also I was not able to reach my backuplights. Yes, I could touch 1 d-ring, but it was too narrow to get it from a d-ring. I decided to take the regulator of my right cylinder, moved a little bit so the bungee was off the valve and wiggled myself further with the regulator in my hand, the left cylinder in front of me and the right cylinder somewhere behind me, but there was happely a 2.10m longhose on it. So after the restriction, I could pull the cylinder back to mee. I also could turn the backuplight on. Then I looked at the mainlight and there was gravel between the switch. I kicked that out with my knive, attached the cylinders to me again and then I found out that the right regulator was giving water. So I had to take the cap of under water, saw it was full of gravel, cleaned it, and could go further in the cave which had really good viz. The way out I dropped both tanks in front of me, not attached to anything. So there was nothing anymore that made the restriction too small. But in here I had several smaller failures that are solvable by staying calm. I have been in that cave several times since then, and yes, you can do it with only 1 tank in front, but only if the entrance is quite wide, not always.
It is the same as the Truffe cave in France, most times you will be able to get in with a twin12, but sometimes not.
And also the size of your body counts. I have tried to get in a cave that is mostly dry caving, but you only need a 3 liter tank to swim the 5m under water. I did not fit in. I have tried and tried, but I was not able to get in. A smaller man could get in, but it was also hard for him. So if people will say it fits, it maybe will not fit for everyone. Also a thing to think about.
And there are cave accidents or incidents known where nobody made a mistake. Just there was bad luck. I have taken divers out of a cave (happely alive as they found an airbell) because another diver broke the line on the way out in zero viz. But he did not know at that time. He realised when the divers did not came out of the cave again. Then there was panic at the surface by a diver who tried to do freediving in freezing cold water to try to find the other divers. So trained in cave diving, did not do anything wrong, but only felt 1 time he was somewhere stucked with a fin, kicked, was free again and then when others were not coming out realised maybe he had broken the line which was true. I was the only person with a ccr onside, took the half empty cylinders of that diver as extra, and started searching. Found the divers in an airbell in an inflow tunnel. They were only 6-7 minutes from the exit, but there was no line going to the exit anymore. Due to really zero viz I took 1 diver out first with touch contact. All went out without problems. I only pee-ed in my drysuit. Then after the dive when all cylinders must go back to the car, one of the divers did it in such a hurry in the heat, he was ill in the evening and the next day. No decoproblems, but just the heat, stress, etc. This example shows that even if you are trained or experienced, you can make strange decisions when you are in stress.
And remember, every human can panic. More trained people are less prone to panic, but panic can happen in every diver. Also in me or any other here on the forum.
And I am a cavediver, but also love wrecks and reefs. I also have done combinations, the entrance of a cave was in the sea, so we did a cave dive first and drained the tanks in shallow in the sea. Also I like wrecks, and even with a wreckdive things can go wrong. Due to group pressure I almost died in a wreck 12 years ago. But I always say now: duckweed will never die.