Recently a functioning dropper elevator stopped working and I tracked it down to two issues:

1) - A dropper will not function when placed at 1821, 5, 3244.  Droppers placed in spaces adjacent to this, powered by the same circuit, function correctly.

2) - A redstone torch placed on top of a block at location 1821, 6, 3245 will not invert the signal in that block.  The torch simply stays on.  If redstone dust is placed on this block, it will illuminate properly to reflect the state of the block.

https://youtu.be/GCgBFRz74Fs

I have tried removing all adjacent blocks and replacing them with other materials.

I am unaware of any changes made to the world between the time when the elevator was working and when these blocks stopped functioning correctly.

I can provide access to the server upon request.

World zip can be found here: https://drive.google.com/open?id=1LGwA6msSR7c0YLnQuycwChUylCRIx99J