[1.76pr4][SMP] Using /clone or /fill renders monitors and computers unuseable

Again another bug post :/

So how this works is if either /fill or /clone is used in THE SAME chunk a monitor/computer is in, it can not be used until the chunks are reloaded.

Reproduction steps:

1. place a computer
2. place a multiblock monitor (easier to see)
3. use /fill or /clone (not replacing the computer and/or monitor)
4. they are now unuseable
5. do /tp ~ ~ ~500
6. do /tp ~ ~ ~-500
7. they are useable again

Dan is trying to track 1.76 related issues on GitHub.