I’m afraid I have no advice for you.
But I will say this: I have yet to remember a single incident reported on this board where somebody was told by Apple phone support to upgrade their macOS to fix a problem and it then actually fixed their problem.
Those guys will tell you to upgrade irrespective of what the trouble is and completely regardless if they even have a clue as to why or how this problem should be related to a bug they know has been fixed in the latest macOS version (fat chance of that, check out Apple’s “release notes”). But it’s the easiest way for them to “deal” with your problem. And on the off chance that it actually fixes something (or gets you to believe it fixed something), they might as well go ahead with it because what else have they got? If they had an actual understanding and solution ready, they’d be giving you that and not pulling out the standard go-to from their call center playbook. It’s the Windows have you tried rebooting it trick translated to Apple. Throw it at the wall and see if anything sticks. 