I'm sorry to hear you're having issues with your V25's rear speakers.
Have you tried testing the front speakers on the rears to see if the issue persists? If it only happens with the original rear speakers then this would imply a problem with the speaker itself. If the problem continues, however, then it may be related to the bass module.
I would also recommend trying another speaker cable as this will also help with diagnosing the problem area.
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