The breakage rate for crafting and harvesting tools is now much closer to their designed specifications, making them effectively more durable than they have been but about as durable as they should have been
When a harvesting tool breaks from use, the tree or deposit will yield at least one bit of CNR before the tool breaks
The check to find out whether or not a tool breaks happen every time it's used, not every time something is returned. So for example, if there's 15 attempts to dig at a deposit before a single piece of CNR is returned, then there will be 15 checks against that tool, not one.
And another thing just out of curiosity. Does this mean that there is a check on the item every time you click on the deposit, or every time your pc says "arrgh, digging is hard" (or whatever the statements are), which I guess would be once per round?