.

Yeah, you gotta make the sector underwater. In deep water, conveyor belts affect floating monsters.

Also note that if there has been sound in the sector where it teleports, it will be woken up upon teleporting there in Boom (and Boom-compatibility modes).

Grain of Salt said:

By "deep water", you mean transfer heights derived from the 242 linedef?

Yes.

I figured this trick out completely by accident several months ago, and I found that you can even scroll and teleport non-monster objects (like candles or powerups) the same way.

This is the only documentation I've ever found about the deep water trick for caconveyors:

Modified carriers to carry no-gravity things at any height, if under water
(so lost souls etc. get carried by currents just like other things on
floors).

It's from LOG_LEE.TXT, in the Boom source package.

The same file also mentions the sound target issue, so it was noticed at the time, but they didn't fix it at the time. (ZDoom did it by changing "soundtarget" from a sector property to a monster property. Soundtarget is what's used by monsters to remember if they've heard something or not, in Doom they ask the sector they are in if they've heard it. So if a monster for some reason wanders into a sector which has heard a player, that monster is instantly alerted. The issue never happened in vanilla (baring some contrived situations based on spawn shooters) but with innovations like conveyor belts, FraggleScript, or ACS it became very possible.)