Issues with PS1 controller via GPIO

[0ps1]

I'm having issues with my PS1 controller. It gets detected, however it only responds to key presses whenever it feels like. It's absolutely random. And when it does, it has a (variable) delay. I've had it working before, did the exact same thing now, but I really can't get it working again. Did everything as usual, installed gamecon drivers, connected the remote (verified the connections), but it's still unreliable. Tried both on my Pi 0 and Pi 1 B, with the same SD card, same behavior on both.

Pi Model: Pi 0 (same thing on my Pi 1 B)
Power Supply used: Same thing with 2A PSU and connected to my router's USB port.
RetroPie Version Used: Tried with an old RetroPie image I had (not sure which version) and with 4.2 downloaded a few hours ago.
Built From: RetroPie images straight from the website.
USB Devices connected: keyboard
Controller used: non-analog PS1 controller (SCPH-1080)
Error messages received: None
Log found in /dev/shm/runcommand.log (if relevant): Not sure if this is relevant? Module runs successfully (ran tail /var/log/kern.log to check) and the controller is detected when setting up inputs on emulationstation
Guide used: Well... My head and this: http://piplay.org/forum/discussion/1354/install-gamecon_gpio_rpi-without-using-retropie/p1 which was the only really helpful thing I found a year ago when I first tried to make this work

I tried on both Pi's with power from both the 2A PSU and router usb port. I checked wiring 2/3 times. I've tried with an analog PS2 controller, same thing happens. I'm not sure what else to do. Thanks in advance for any help.