Since this kind of problem can be caused by an internal failure of a defective IC (these are really tough to find while it remains intermittent) or something as simple as a poor solder bond, probably occurring during during automated (wave) soldering, it will be 'cured' by a tech with little knowledge by replacing a major board at a high cost.
If it was my Ilo (yeah, got one too), I would remove the main board and inspect it under magnification and with a hot, clean soldering iron at hand, I would 'shotgun' the area of the audio circuitry. In order to troubleshoot this to a bad component, it would be necessary to wait until the failure became constant or have a couple of cans of freeze spray which can often reveal the precise location of a bad solder bond or a flaky IC.
It is unlikely you will find anyone servicing Ilos since the company is bankrupt and replacement boards will be difficult or impossible to obtain.
I check with the website below now and then to see if they have parted out any sets made by Ilo and this is probably the best course for anyone owning these orphans (thanks, MallWart).
If you are a logical person or know a friend who has some background in electronics, it should be possible to determine which board is the likely problem (hint; tracing backward from the speakers will help), then doing a search on the assembly number of the complete board may find one but if new, it will be expensive so check Jimmy's inventory first since they ask about 40-50% of new price for their parted-out boards.
Jimmy's Parts
I checked and the link contains the search term 'Ilo 3200 HD' and there is very little on hand at this time.
Good luck-