Computer won't sleep, my monitor wakes up my computer

I recently purchaced at T232HL for my PC. It was working fine, now whenver my PC blanks the display or goes to sleep the monitor starts looking for another input then wakes the PC back up.

The computer is plugged into HDMI1, when it goes to sleep the monitor tries HDMI2, VGA, then back to HDMI 1, then displays "No Signal", the amber light comes on briefly (0.5s) then the screen comes back on to my lockscreen with the PC wide awake.

Using powercfg -lastwake I can see that a USB device woke up the computer. I tired unplugging each device 1 by 1 and found that when the USB to the monitor is unplugged it goes to sleep without issue (it still cycles inputs, but doesn't get woken up in the end).

What's going on here? I don't think the monitor was cycling through input when I first started using it, and it certainly wasn't staying awake. Any hints on how to prevent auto input searching and preventing the monitor from waking up my PC?

Thanks

-Ian