What about redoing someone else's repair that could have been done better? Is it Possible? Maybe.
There are many things to consider when performing a re-repair.
First, Are the flaws more structural or cosmetic? Two star legs that have not been filled could be a cracking problem and might be worth the time and money to fix. However, a little black air bubble in a bull's eye might be better to leave alone.
Second, is there a way to get new resin into the break efficiently? Sometimes you can just pick or drill out the pit filler and create a new route for resin to flow. If the main pit has been closed off, and there are several little chambers of air left, it might be best just to leave it alone. On the other hand, we have actually drilled holes at the ends of several unfilled star legs on the same break and got resin to flow. In the end, use your judgement on what is feasible.
Third, How much improvement can be achieved and will the time and cost be worth it? In the end, make sure you are doing more good than harm, and that the cost that you must charge your customer for your time is worth the added benefits that you can provide. Fixing someone else's work isn't always easy, but it can be done. It can also make you more profits and build your reputation. Just choose wisely on how to go about it.