Barry I have been building MU since about version one, I don't remember ever having that problem with single or MU.
they may have went back to 100%, but then it was all sounds. This is just engine and accent sounds on all my engines even when I run single locomotives. Only two sounds in that whole menu of sounds go to default of 70% ! that don't sound right. all other sounds keep there 20% setting horn, bell, etc.
Hmmmm