I'm beginning to see more and more of these TS-H943 drives not ejecting.
After cleaning and fully greasing up the mechanics of this drive it would eject ok if orientated horizontal but not if vertical - all with its top cover on. If top cover off, no problems at all.
The consensus (reading around the place) is that the rubber belt that drives the mechansim which ejects the tray (which in turn breaks the magnetic seal) is worn and doesn't have enough strength. Replacing the belt with a new one should fix the problem.
Sure enough, new 19mm belt (slightly smaller than original) fitted and drive works perfectly. Confirmed this fix on 2 problem drives I have here.
For people in the UK you can get these belts at Maplin, order code: FD36P @ £2.98ea (rip off) They are about 30p ea if you can get them from RS/CPC/Farnell etc...
Its possible to replace the belt without even opening the 360 case (if you can get the tray open) as its right at the front of the drive and fully accessible through the gap in the tray.
neildo.