This is not even just for open-source applications. It's happened often over my time at my current job that a client will report a bug and then we'll be unable to reproduce it. At which point, we don't waste time trying every possible thing, we ask for the exact steps they took when it happened. If we
still can't reproduce it, we schedule a screen-share meeting with the client so they can directly reproduce it on camera for us, and we can walk them through gathering info for us (exact steps, network traffic, console errors, etc.).
If it can't be reproduced, it can't be debugged or fixed.