Hi, I have a Samsung A71 which I got on the 2nd of June this year, so still in warranty.
When I am listening to videos, either through Facebook, YouTube or twitter (any service tbh), I sometimes get a crackling noise coming from the speaker, then the sound goes very feint, then sometimes goes off completely. If I tap the back of the phone on the bottom right hand corner, this sometimes rectifies the problem.
The phone has been wiped and sent back to Samsung three times now, with them not finding a fault. Finally a WeFix appointment was made, and the speaker and charging point were replaced, however, the original problem still persists.