Why do my speakers only work sometimes?

After having the battery changed in my Pixel 5, the speakers seem to work intermittently. Sometimes they work totally fine. Other times I get fuzzy audio. And then there are times when I get no sound at all. The microphone also seems to come and go. Usually if I restart the phone, I get good audio again for a couple of days. Then the problem returns. Alarms, phone calls, video calls and media playback are all affected. It seems odd that it can work fine for a time and then stop working and then work again after restarting. Anyone have any suggestions as to why? As I say, this problem coincided with the battery being replaced.

Much appreciated.