Earlier today I had a couple of people complain that they had made purchases and not received their products.
I checked into it and discovered that the grey goo fence is preventing the script from giving inventory to the purchasers. The scripts have delays built into them and only distribute 1 product/package per purchase.
The vendors in question hadnt been used excessively so it's not an issue of a particular vendor being blocked but I believe all of the vendors put together causing the problem, eg - 5 different product sales = no more distribution
I have put in a bug report but this and I realise that you're trying to prevent the grid attacks but I'm guessing that this will affect a lot of people without them knowing why or what to do about it.
ps. the bug report field is too short