It would help if you could upload the afphoto file.
however, i can reproduce the issue by using Layer FX, Gaussian blur on e.g. a vector shape.
The issue is resulting from partial transparent pixels. You need all pixels full opaque to avoid the issue. The best way to achieve this depends on the actual document content, e.g.:
adding a Channels Adjustment, select Alpha, set offset to 100%
add a fill layer with suitable color as bottom layer
