The Silderglass Tunnel's end reward was not paying out as intended. It was meant to reward up to 10 Silderglass at 50% tunnel stability, but in reality it was capped lower than that.
This has been fixed and adjusted. The reward now scales from 3 Silderglass at 0% stability up to 15 Silderglass at 80% stability, with higher tunnel stability giving higher rewards.