Mob Spawning issue: natural spawn hostile mob grinder not working afk

I just returned from a 1 year break from EMC, and upon returning, i went to my outpost hostile mob farm. The farm uses tripwires and pistons to remove the floor block when hostile mobs spawn, and they fall to their deaths. But now i try to afk at it and all mobs stop spawning as soon as i go afk. I checked the wiki and found nothing about afk mob spawning changes, can somone shed some light on my problem? Thanks

There are new rules about what mobs can and cannot spawn on. (This is Mojang's changes, not EMC only). But I'm positive that just tripwire still allows them to spawn. What do you have under the trip wire?

As an example, my old gold farm turned to junk because the new MC spawn rules didn't allow mobs (pigmen in this case) to spawn on pressure plates anymore.

my spawner is set up that they spawn on normal blocks. and the farm works perfectly until i stop moving for a bit, then slows, then stops altogether

the mobs spawn on slabs

Slabs will generally prevent a mob from spawning, so I think that could be causing these issues.

Slabs work fine , as long as they are not on the bottom half of the hit box. (unless something changed that I don't know about?)
Th reason to place slabs instead of full blocks is to prevent bats from spawning underneath the spawn spaces and raising entity count.
Farm seems to be working a bit better now, but items drop insanely slow. 10 hours at the farm yields less than 8 stacks of each item.. This is less than half of what it did in 1.8. We're mob spawn rates adjusted down again? I looked everywhere, and found nothing in the wiki about it

Is it a shifting floor design?

What is /encount when this happens?

Entity count not an issue. This farm relies kills within 1 second of spawning. Enter count is less than 20.i.have some villagers there and they account for most of the entities

hey I know this is older but my outpost built a mob farm that uses pistons and tripwire. it works and is slow sometime doesnt seem to work but it does. these farms work better when mobs havent been messed with like in single player minecraft. the one we made still produces more gunpowder an hour then the witch farm on smp 8. if you want to check it out let me know and ill get you the cords to it

mobs stop spawning when you go afk

Not true. I Afk at my wither skeleton grinder and come back to it being full. Also i talked to Aikar a while back about it and he said he was going to implement the feature but it was cancelled because it'd cause drama with Afk farmers.

mobs still spawn when you are afk otherwise my farm would not work. I do think spawn rates drop though. but not 100% sure if they drop or not

yes tru, test it out

my alts afk at my gunpowder farm and has been afk for most of the day. creepers are still spawning and have the whole time ive been afk

Hi MrClydeBarrow, could you share your gunpowder farm design? I'm looking for something that works well on EMC!!

this is the design we used. https://www.youtube.com/watch?v=cOD_btn0dtI
it only works in deep ocean biomes. we arnt 100% happy with it but we get gunpowder faster then killing witches at a witch farm. other thing spawn with this farm too. its not a creeper only farm like it says it is

Those witch farms seem to only give 3 witches every minute or so... It is creeper farm really that bad?

it was worth building and I only use it if im going to AFK otherwise it gets pretty boring to watch

Make one of those afk water spinny thingies so u dont go afk cuz ur constantly moveing