Quality is delighting customers
I think you must capture it with proper screenshots and notice on what are the input fields when this kind of bug is generated. In this cases tester responsibility is to understand the cause of the issue and then only he can report it to developer
It is difficult to convince the developer with this kind of bugs, these kind of bugs are called incident bugs.
1. Capture the screen shot of the bug
2. Make a note of the steps which you followed to generate the bug
3. Give more information about the bug, so that developer can fix the bug
4. Inform to manager or Team lead and seviority of the bug which will impact on the application and business
Rest is developer and manager's call when and how they want to fix the bug.
We don't have shortcuts to convince the dev. team, We have to reproduce the issue in-front of developer. This is the best way or else at least we should provide minimal inputs to trace the issue (Ex: Screeshots, input data, specific scenario, checking the error log immediately when error occurred...etc)