I'm assuming for a completely different reason (than whatevers causing her crackling) but I have the exact same issue Tony. After a little while of having the 4k player on I get strange crackles through the speakers.
Nothing else does this, not my Zen, not my TV, not even streaming to the Vena from my phone via Bluetooth. Only seems to be the 4k player that does it, and it does it whether it's a disk I'm playing or I'm streaming Netflix or using a HDD on the player.
The crackles aren't RFI or EM interference as far as I can hear, it's a very distinct and loud crack and pop every so often.
Very strange but I think in my case the player is on its last legs as it's having some minor visual hiccups as well as Netflix issues too.
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Hifi: Innuos Zen Mini MKIII > Fisual Hollywood Optical > Quad Vena II > Custom Clyde interconnects > TA Monoblocks > Tellurium Black > Reiver Millburn MK II (Custom super tweeters & TQ Black Jumpers).
Headphone Rig: MacBook Pro/Google CCA > Fisual Hollywood Optical > Beresford SEG > Custom Clyde interconnects > Beresford Capella > Sennheiser 700s