Incorrect children returned on facet query

When I query for child documents like

&fl=id,priref,[child parentFilter=parent:images]&fq=database:"images"

Everything works ok the correct children are returned.
Now if I add a fq parent which filters on children:

&fq=

{!parent which="parent:images"}

geo:[38.671875,-101.25 TO 41.30859375,-95.2734375]

Suddenly I see incorrect children being returned.
{
"id":"images_397",
"database":"images",
"childDocuments":[
{
"database":"artists_child"
}

This child document belongs to a different parent record.

If i change it to something like:

&fq=

{!parent which="parent:images"}

(database:"images_child" AND geo:[38.671875,-101.25 TO 41.30859375,-95.2734375])

It does seem to work but obviously it shouldn't behave like this.