I confirm I am having the same problem. Items up for over 24 hours without selling, then I delete one of the items from the market and the others get sold fairly quickly. This has to be a bug.
It is an issue they're aware of and working on apparently. As someone else said, after a couple of days "Daniel" buys anything sitting unsold so it's worth listing things for the maximum price you can. Then at least if it takes a while you get rewarded.
