While soldering a PCB I overlooked a spot where some excess solder had bridged two pins. When I connected the PCB to my raspberry Pi, the Ethernet and activity lights slowly dimmed to off, and the Pi was no longer reachable over the network.
I disconnected the Pi and connected the PCB directly to a bench power supply, to test it standalone where I noticed the high current consumption. I flipped the PCB over, and finally found the short, and removed it. On power up, there was no high current consumption any more but all the outputs on the PCB were high. Removed the chips, and tested the PCB on its own, which seemed to work okay.
I replaced the chips with new ones, and everything worked fine ... Turns out my Pi survived the ordeal as well.