The process is stated by others above, perhaps not completely. Let me attempt to summarize:
1: Switch speaker cables. If it happens to left speaker and not the right (problem reversed) the problem is upstream of the speakers If the problem does not occur in the left speaker, then the right speaker is the issue.
2. Check and clean all wired connections. Check wires for visual and electrical integrity If the problem is not solved, proceed below.
3. Clean the volume control and balance control if they are a physical and not virtual control (nob vs iPad as an example). See if the is not solved, proceed below.
4. Look to your source or amplification. Verify output/input maximum voltage specs to assure you are not clipping the inputs I do not think it’s this but it’s a good check. If this does not solve the problem, switch out components to determine the bad actor. Send the component for service.
if i were a gambler, which i am not, i would bet on #3.