Possibly this has been raised before, but I didn't find it on a quick survey.
I bought an approx. 1895 48 button Lachenal EC last September. It has brass reeds. In general, I'm very happy with the feel and sound of the instrument, given that I can't justify paying thousands for something more upscale. I've been gradually wrapping my head around the EC fingering (I play accordion).
After about a month, one reed, the G2 (low G on the left side) went flat. Consulting with the seller, I filed it to tune, but soon it went flat again. After a few tries it would only hold the tuning for less than an hour. So the seller supplied me with a replacement reed. I got that in January--all great. It played fine until last week. Now the same reed is going flat again. Again I tuned it, but it's not holding. Why does it go flat, and why this one reed out of 96? What is the solution?