Problem: Recently I faced the issue with my Jabra Elite InEars that while I was using them, the volume started to continually decrease until I had to max out the volume on the phone. Yet the sound was still barely loud enough to hear it. After not using them for a while, sound was okay again (still quiet but better) until volume started to decrease again while using.
The internet is FULL of advice about Bluetooth settings, resetting the phone, entering developer mode etc. Yet it was ways easier.
Solution: In the end I just had to clean the little hole between the contacts and the ear plug of the inEars! This hole might be dirty, blocked, etc. Just try cleaning it with a needle and the sound issues might go away.
If this does NOT help, check the other Jabra post(s)!