The luck check occurs once you start digging up the chest and only occurs once. As for the bug issue, if you want to detail the steps you took to have this issue you can email them to [email protected].@Kyronix I usually Pre-mark runes to my map locations then hit the luck statue later so I can get more done per night. Am I losing out on the luck bonus by partial digging and marking runes?
Also, there seems to be a bug where an unreachable 'extra' metal chest spawns below ground where you dig sometimes. You can see it using the object handles.