Spontaneous refermentation in bottle?

[drubes14]

Hey guys - came back to a case I had bottled (keg carbed) about 2 months ago. On one or two of the bottles, it looks like someone shook the beers up. There's a bubbly head on the top. I know no one has touched them. Photo below.

I had cold crashed these puppies and force carbed them so no extra sugar added. Fg was like 1.011, and it had sat in primary for 2 weeks after fermentation.

Anyone had a similar spontaneous almost rekrausening in bottle? I've been brewing for 10 years and have never seen this. Only 3 bottles of 2 cases are like this.

 

[Qhrumphf]

Chill one if you haven't already, and give it a smell/taste. It may be nothing, just micro temperature differences and trace sediment allowing dissolved gas to nucleate. If it's only 3 bottles out of two cases, the cleaning/sani on those bottles may have been lacking.