Just report the problem you are running into. Do not worry if something similar is open. More examples is better!
This strategy has a couple of underappreciated benefits.
As more comments and debate pile up on an issue, it becomes harder and harder to resolve. "We resolved the original issue, but what about the three incomplete examples shared in the comments? Are they fixed too? Are they even caused by the same root problem?" Suddenly you are cross-referencing some long internet debate instead of working on fixing problems.
If instead all of these people had opened separate issues with their own SSCCE, it would be way easier to figure this out. Is the example still broken?
Piling on to an existing issue tends to mean we only have one viable SSCCE to work from, even if lots of people are experiencing the problem. This can make it harder to figure out the root cause.
Having many examples is just better! The clearest example is usually not the first one, and as more examples get shared, you start to get a feeling of what is common between them all.
Someone has to decide if issues are the same or just similar. Why would that be the reporter? The core team knows a ton about the implementation, and it is often much easier for them to make this determination. Reporters would need a lot more time to make such a determination, and in practice, they are much more likely to make mistakes.
Say you have a car problem and take it to a mechanic. Imagine if they would not accept it unless you could correctly identify cars with similar problems. What? Just fix the car.