It maybe worth self troubleshooting by going over to your dial pad and type in *#0*#, this will bring up a number of tests.
That and or visit a Samsung Experience Store or Samsung Service Centre for a diagnostic.
Current Phone ~
Samsung Note 20 Ultra 5G SM-N9860_256Gb SnapDragon 865+
Samsung One Ui 3.1/ Android 11.
I performed that test before and it works flawlessly during the test. The speaker randomly stops working or switches to one speaker only (top or bottom) during the call.. not immediately at the start of the call. I feel it's more of a software problem than the hardware
I too am having this issue. Its very annoying.
It happened to me the other day while I was using DEX. I was docked in on my DEX puck on a phone call, with the speaker on. I recieved another call, so I opted to put my current call on hold, while I took the new call. Speaker phone was still on for the duration of the new call. However when the new caller dropped, and the phone switched back to the call on hold, the audio was no longer on speakerphone. Get this, the speakerphone icon was still lit green to show the speakerphone setting was still on. However the audio was clearly not on speakerphone.
Usually I would just toggle the speakerphone setting on/off, and that would fix it temporarily. What further complicated my experience is DEX doesn't allow you to toggle the speakerphone icon during a phone call, while in DEX Mode. So the only recourse was to hang up and dial again.
Samsung, Please fix this.