Sadly I had battery drain issues with WireGuard on Android. That's why I'm content enough with the native DoT feature.
Perhaps a kernel is available for your device, or you can look at building and contributing one if not!
What device do you have?
I'm not affiliated with the WireGuard project, but I would appreciate it if you could encounter the issue again, and then submit an account of your experience and the logs from your device.