So since both fence collision based ones and door collision based ones broke I sat down and figured out a piston based item elevator. Clunkier and for certain noisier than the previous ones, but I don't see any immediate reason that this one should break like the other ones since it's not based on a sub-block collision mesh.

If you prefer a written explanation, basically I used two pistons to smash items upwards into the elevator (which is solid just like before). The initial version used a clock and pistons to gate items and make sure they got timed correctly - this causes a bit of lag. The newest version uses a tripwire and two separate waterstreams to create a completely clockless, no water update version.

I've tested it a fair bit and have yet to lose a single item.

There's now also a second, clockless version designed for minimal lag - when the elevator is not running there are no updates, and even with the elevator running there are no water updates anymore. The world download contains both versions.