I think plain and simple it is water sitting in a tight little crevice that can't drain out and doesn't evaporate quickly. Just a good idea to try and avoid that when possible. I also don't have fans running near the few orchids in my home like I do in the greenhouse. So good moving air would be helpful. In our climate, humidity isn't high so it's not like it was a damp humid environment or anything. It's an open, well lit room with a ceiling fan on low in the distance.

I dunno, there is something that niggles with me over this, and I can't put my finger on it. Phals are really meant to grow bare rooted, let's face it, and media around them is artificial at best, and a hinderance to good growing at the very least. We know that a medium that is too compact and wet will kill the roots, and cold will screw the plants for sure. I can understand that a plant that already has several strikes against it might find that the additional wetting might be a strike too far.
My question to you would be, how many phals do you have, are they all watered in the same way, (ie occasionally getting the crown wet) and how many get crown rot?

I only have 7 at the moment but used to have a lot. I don't usually have a problem with crown rot as I am fairly careful. Just this once.

I still say, yes Phals grow bare root in nature, same as Catts and many other genera. Potting, if done well for our situation shouldn't be a big problem. Millons of orchids survive and thrive this way. It is the only practical solution for most orchid growers who don't live in the tropics with trees to mount them on. It is the upright position of the plant which fails to allow for proper and fast drainage of water compared to the way they hang down in nature out in tropical breezes. That's my :twocents:

Like I say, one in a winter doesn't seem like a reliably causal link, that's all.