If I remember right, they started to have this auto ban system with this transferring because people get scam.
Some people remove their items just before confirming trade, so they added some warning and this auto ban when nothing was on a side.
To avoid this, people started to add some trash gears when transferring.

This story is from 2013-2018 before I stopped playing once. Not sure how it has changed since then but maybe this would help.