As we get a lot of useless troops, park them on the chest spawning tiles of mines that give tier 1 or 2 junk. Eventually some of the other mines will give higher quality stuff. This is how I managed to farm radiant gems... Something in the chest spawning is not working as intended... but rather than the Dev fix it, I think they need to find a better way to implement.
For example, all sovereign gets 1 random item per resource node. Wiz & Guardian`s skills enable to get 2 units, while the tinkerer would get 3-4. Instead of spawning chest, you get a summary at the start of your turn indicating you get stuff. However, they would need to rework how tinkerer can get those freebie skill and lore points (from losing the chests).