Hi,
can you clarify what it means when you changed mtb:scale=0 to mtb:scale=0-1?

An invented value like 0-1 will likely not be understood or used/rendered.

If you believe the trail is harder than mtb:scale=0 but not as high as mtb:scale=1, so you want a finer separation, you can consider using mtb:scale=0+ or mtb:scale=1-.

For help, read the wiki at https://wiki.openstreetmap.org/wiki/Key:mtb:scale 