The items contained within random boxes, and all other random mechanics in Nine Dragons, are based upon fixed probabilities, which are verified as part of the testing/QA process.
There are no "bad luck protection" mechanics for random boxes - the odds for any given result are the same, whether you have opened one, ten, or one hundred or more boxes in a row.
Any truly random systems will be prone to strings of unlikely events, such as a flipping a coin to the same face ten times in a row.
If you still believe that there is an issue with a certain random mechanic, then you may report it to us via the support system. Please include as many details as possible, and be advised that we can only act if a verifiable issue is found.