Why is one speaker quieter than another (CM) on a computer?
In such cases, "contact phenomena" are almost always to blame. You have already written about the wire yourself. By the way, it is not a fact that the vein is interrupted in it, most likely the problem is in the soldering on one of the connectors. Alternatively, the braid may touch one of the signal contacts, which is why one channel is short-circuited. A fairly typical case is poor contact in Jack connectors, especially if the plug is not gold-plated, but ordinary. It is "treated" by wiping the plug with alcohol and rotating it in the socket. With a "hard case" - bending the contacts in the socket. A software or hardware jamb, so that it affects only one channel, is very unlikely.
Test the speakers on a different audio source - for example, on your phone, if there is a similar jack. If the speakers give the norm, the problem is in the sound card of the computer and most likely in the socket.
Most likely the problem is inside the column. Perhaps somewhere the contact fell off due to a microcrack in the soldering or one of the filter elements failed, if the column is multi-band. It is necessary to disassemble, inspect the installation, check the capacitors in the filters. For some reason, the speaker may fail, t.ch. they are also better to call.
check the settings on the computer, maybe the balance got lost, or you have the right channel dead, I have only the left one playing on the laptop, I had to redo the wiring for the left channel, redid it and evenly play everything. so I think that you have some kind of channel out of order
Try to swap the speakers in places (instead of the left, connect the right one) If everything remains the same, then check the sound card on the computer. Connect headphones to the same output. If the headphones will work the same way as the speakers, see the sound card settings on the computer. I had the same problem - there were faulty speakers.