This is a total shot in the dark, but your issue sounds similar to this one (CircuitPython troubles and flyback change | Details | Hackaday.io).
I did not get this to work reliably, so I switched to the Micrmod Ecosystem together with the PoE Ethernet function board.
Just curious. Did you try the hack of adding a bigger capacitor to delay 3.3V supply poweron that was described in the post I referenced?
No as I need a working stable solution âout of the boxâ (if all testings are fine, we will produce several of such devices; its not feasible to require âhardware hackingâ).
Yup!
I havenât seen this problem with my PoE Featherwing + RP2040 stack, but they are designed to work together. If the problem was really a common enough one to motivate a change to the UF2 bootloader but you were still seeing it then maybe the root cause isnât really addressed and I should keep an eye out for it biting me, too.