Those from refusals are very normal.
Anything that has been in contact with fuel or oil is classified as dangerous cargo wich need special treatment as well as special documentation, doesn´t even matter if shipped by plane or ship.
No major shipper will offer the time and responsability for shipping such item.
These rules have been there for a while, but enforcement as well as awareness of these rulles, and more specifically what they apply to, has in the last few years had a lot of focus and attention by controling authorities.