XPS 15 9550, wakes up from sleep after a few seconds

When I shut the lid to my XPS 15 9550 (warranty expired on 11/10/17) and press the sleep button, it will enter sleep mode for about 3 seconds, then immediately wake up. Any idea on how to fix this? It's getting incredibly annoying. All drivers are up to date. Hybrid sleep is switched off and wake timers are disabled.