So, I was in Western Skyrim, doing my surveys, and I started to think I was going nuts, because when I had multiple copies of the same survey, they disappeared. So, I checked and screen capped, and yes, they are disappearing.
Here I am at the woodworking survey, ready to harvest. I have 2 woodworking surveys in my inventory:

I then harvested the nodes and checked my invent again - both surveys are gone:

This is a MAJOR bug for players who do survey writs. I realise that I lost 1 Enchanting, 2 Blacksmithing. 1 Woodworking, and 1 Alchemy survey because of this.
I had my companion, Mirri out at the time. I have not checked if this happens if she's not there. I don't want to lose anymore surveys!
@ZOS_GinaBruno Do you know about this bug?