Sphagnum moss is just so tricky to use. I use it almost exclusively because I am growing underlights. Inside, under lights, lower humidity because of winter heating can wreck havoc with your orchids.
But the bright side, assuming one can find a bright side using sphagnum, is that I have learned how to best use it. Once dried out, it can be troublesome to remoisten it. For me I find by taking the chill off of tap water and watering dried out sphagnum that way makes a noticeable difference. I water with 85-95 degree water and it seems to help. My cold tap water now is 38 degrees F. 38 to 85 is a huge difference!
Plus I have gotten into the habit of trying to make sure that I properly pack it around the roots. Not too loose that water really pours right through it when I pot water nor to tightly that it blocks water flow through the moss to the plants roots.
Sure, it takes more time but I watch the drainage flow through every single pot filled with mostly sphagnum. I think that now after 20 years of using sphagnum for certain orchids, I am finally getting a grip on how to use it, and water it correctly.
My collection is 85% Phrags., Bulbos and Phalaenopsis so I use a good deal of moss.