I saw the lovely new animations for the spanner on twitter and thought that machine repairs could be made more interesting still. I would like it if occasionally various parts of a machine broke down and needed new components to be repaired. These component repairs could be outright prevented by regular maintenance (tightening with the spanner) but could occasionally require new cogs or tech fragments if the damage passes various thresholds. For example, a machine past 50% may need a new cog to repair better than 50%. At 80% damage, it may burn out the tech fragment, and need replacement. At 100%, the machine stops working until you replace all broken parts.
You could even add incentives to keep your machines in good repair, like at 50%, production speed is slightly reduced due to damaged cogs, and at 80%, you lose the ability to mass and bulk craft due to the tech frags or components burning up.
Not to mention, this would add extra trade value and consumability to the little used crafting materials needed to make most of these machines.