This is something I used to have happen but haven't for quite some time, it may just be chance but I know what I do now compared to then is leave the net in the water with the fish in so it can compose itself before being hoiked out onto the mat, and as I'm doing this it gives me time to breathe and then I tend to check if the fins are flat to the fishes body and its dorsel doesn't look as though it'll get stuck in the net.
This may well be what you do and it still happens , so just ignore me if that's the case!! Good man for asking about it either way, I feel quite bad when this has happened to me