Photoshop CC 2019 Corrupted file

Hi
I routinely work with large files saved in psb/large document format) up to about 4Gb with no problems.
I have a file, which is much smaller than the usual PS size that Im used to working with - 1.5Gb, but wen I used a smart layer, and the path blur, I first got a small grey rectangle on the final image. I had done this operation with no problems several times previously.
Now almost all layers in the file have been sliced with grey squares - please see attached reduced size image.
I've had similar previously when working with a smart layer and path blur - the combo does not seem to be working correctly in some circumstances,
Can I recover the file, or do I have do start again?
Many thanks
