Pi4b heats up when connected to OpenWrt router

Hello. I've recently got a Netgear WAC124 router which is now running OpenWrt 21.02.2. Everything seems fine, but I noticed an issue with a Pi that's connected to it.
The Pi is heating up when it's connected to the router directly, either with an Ethernet cable or Wifi. The problem goes away if there's a switch (TL-SG105) between the router and the Pi.
While connected to the router directly, Pi's idle temp is ~51C, but when connected to the switch ~38C.
When I first noticed this, the Pi was connected directly to the router via cable, so I disconnected the cable and made it connect to the Wifi instead. I thought maybe the router it's drawing power from the Pi via the cable. Checked it's temp after booting and it was 42C, but after a few minutes it went to back to ~50C.
Could someone please help me make sense of what's going on?

I do not think the router is drawing current from the RPi, that would be very strange. But there could be some traffic, that the switch is blocking (IPTV / Multicast / ...), that makes the RPi work harder, even if it seems idle.

This is the most known design fault there is of the whole RaspberryPi4b product.

It will cook just by turning it on.

Just google “raspberrypi 4b heat problem”!

It is simply to much computer with to little cooling (no cooling at all to be exact!) after RaspberryPi3 was retired.

I have mine in special Argon cooler cases.

I'll look into this, thanks.

Mine has full body heat sink. I wouldn't power it on without it.

So I found out what was the problem. In order to hide the power bricks and wires from the Pi and the router, the Pi itself and it's ssd, I used one of those round tin biscuit boxes in which I also stuffed an extension cord to power the devices. Bad idea.

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