Its been a month since I'm facing this weird issue with my Samsung galaxy s9 plus stereo speakers.
Sometimes when i play music or anything on my phone...the volume of it gets really low and when i try to increase the volume...it shows that it is already maxed out. This is a software issue because when i restart my phone the issue goes away...i don't really know what triggers this kind of glitch but it is really annoying. If someone has a solution to this issue then please let me know.
Try to boot in safe mode To do this press and hold power button then press and hold the power off option then press the safe mode then check speakers are working or not. if issue persists then Try to reset the settings To do this goto settings then general management then reset and then reset settings. Then also issues there goto a samsung service centre