I'm seeing these every now and then and I have some thoughts to share. As always, feel free to disagree. I feel pretty strongly about this, but I'm open to discussion.
If the answer you're going to write boils down to "never happened to me, start from scratch/buy brand name hardware", then you probably shouldn't be answering that question. OP doesn't need your expertise to know that they can re-do their work or throw more money at the problem. They've asked the question because they want to avoid that. If there's no satisfying solution, they would like to at least understand why so they can avoid repeating their mistakes. If you have neither the solution nor explanation, then your would-be answer won't be helpful.
Exceptions probably apply, but please think twice if what you have to say warrants making an exception. You can also consider leaving a comment instead. It won't get you any reputation, but that's not the goal - helping OP is.
Another thing to think about before posting an answer if you can't explain what OP is observing: is this really within your area of expertise? Maybe they're doing something similar to what you were doing for years, but they're using different software and you don't know its quirks? Maybe they're using the software you use, but you've never used that particular feature and you shouldn't be posting your guess, or at least you should make it clear that it's a guess and not a confident answer? Our knowledge and experience, even if broad, are still limited. It's important to know where these limits are. Speaking from the position of an expert without having anything valuable to say only dilutes your reputation.
Please also consider the fact that your well-meaning and confident answer may encourage someone to start redoing their work or buy new hardware before a more experienced user can post a better solution.
Finally: if you feel the need to delete an answer almost immediately after receiving a downvote, before I can finish typing an explanatory comment, then I think you should reflect on it. Do you have so little confidence in your answer's correctness? Maybe you should make that clear in the answer. Are you afraid of it getting more downvotes and losing you reputation points? Maybe you should have higher quality standards for the answers you post.