Loud rhythmic humming on stacked Quatro 10kw inverters

[OffGridDave (Dave)]

I have an install where I have 4 10kw Quatros in a split phase configuration. The problem I am having is when the inverters are using the grid to charge the batteries (6 ea. 48 v 200Ah) when the inverters switch from bulk to absorb, the Inverters start a loud rhythmic humming with a “Ticking” sound. The sound is not heard when in bulk charging.
Has anybody had the same issues, and if so, how was it corrected.
Thank you for your response.
Dave

[A-P]

Can you upload a recording? I have the same configuration, of the same inverters - happy to compare.

[Westphal_Solar (Perry Westphal)]

Hi, I have a humming sound on a QUATTRO 48/15000.
Is it the same?

Quattro 48/15000 Can anyone identify this sound? Is it normal?

Hi everyone, I am an authorised Victron installer on Ibiza. I’ve got a short clip of a sound coming from a Quattro 48/15000. Installed around 4 years ago. I’m not sure if it’s normal or if it indicates a problem. Does anyone recognize this sound or know what might be causing it? Any input would be appreciated! [Attached the audio clip] Thanks in advance!