Hi Tom,
You'll be able to add a daily rain edit tomorrow to correct the daily rain as far as your stats go but looking at your Wunderground data, it looks like you got a huge amount of rain between 04:12 and 04:17 and the wind picked up considerably for a few minutes around this time (looks like a cold front coming through - there's a rapid temperature drop afterwards). Is it possible the rain bucket was being buffeted by the wind?