Hi Andy,

The only thing I can think of is that one of the cables could be suspect or a possible problem with the I/O board on one of the speakers...

Have you tried re-routing the cable to the 5K's? Just ensure it does not go anywhere near mains cables.

Also, try swapping the 5K's and re-type them (i.e. Left Slave becomes Right Slave and vice versa). Could be the I/O board on one of the 5K's playing up?

Not sure what else to suggest...

Please keep us posted.

Cheers,

Steve

Main: 861v6 (LPS), 808v6, UHD722, DSP8000SE Anniversaries, DSP5200HC, DSP7200.2, SW1600, Sky Q, Cambridge Audio BD, Roon, M80
Office: 861v4 (LPS), 818v3, 800v4, HD621, M&K S150P, DSP5500HC, M&K MPS2810 sub x2
Son's system: 861v4, HD621, DSP6000.2, DSP5k.2C, DSP33, F80
Spare: MCD, 100 Series, 200 Series, 500 Series, C15s.