Having issues with Enderman placing grass blocks inside the water tank even if the Multiblock is already completed.
Unable to place any lighting inside to prevent mobs from spawning. Would like to know if this is an issue or this is expected?

Ya already tracking mobs spawning in multiblocks in #6730 (haven't had time yet to look into it given in theory they shouldn't be able to). Leaving this issue open for more specifically looking into if there is a way to stop where endermen can place blocks/teleport to, though it may require me to make a forge PR if there is no hooks currently exposed for it.

Maybe fill multiblock structures with fake blocks like BedAir?

Any workarounds I can apply for this? I dont want to let my Boiler disconnect from my fission reactor that would cause it to go boom randomly.

Industrial Foregoing's mob slasher is OP.
Also fission reactor has redstone ports. Redstone controlled ultimate pipes themselves can store enough water to cool down medium sized reactor. You can also make thin value under reactor itself to provide extra stop water. Just make it not connected with main volume. There's always a way, except when there's no way.

Any workarounds I can apply for this? I dont want to let my Boiler disconnect from my fission reactor that would cause it to go boom randomly.

Industrial Foregoing's mob slasher is OP.
Also fission reactor has redstone ports. Redstone controlled ultimate pipes themselves can store enough water to cool down medium sized reactor. You can also make thin value under reactor itself to provide extra stop water. Just make it not connected with main volume. There's always a way, except when there's no way.

Thing is this is sodium cooled reactor water isnt going into the reactor its sodium which means its the going to go boom regardless because the boiler isnt accepting any super heated sodium from the reactor

Putting this on hold for now until something like MinecraftForge/MinecraftForge#7548 gets merged which should make it a lot easier/cleaner for me to deny endermen from placing blocks inside of multiblocks.

Would like to add the following details. Built an 18x18 Thermoelectric Boiler and a 17x17 Turbine Reactor. So far the Thermoelectric Boiler spawns mobs inside even filled with it filled with water. Checked both the Water Tank and the Steam Tank. For the Turbine Reactor, a Grass block was placed on the upper half of the Turbine but it only occur once and haven't experienced again.

Ya already tracking mobs spawning in multiblocks in #6730 (haven't had time yet to look into it given in theory they shouldn't be able to). Leaving this issue open for more specifically looking into if there is a way to stop where endermen can place blocks/teleport to, though it may require me to make a forge PR if there is no hooks currently exposed for it.

Any workarounds I can apply for this? I dont want to let my Boiler disconnect from my fission reactor that would cause it to go boom randomly.

1. this made me laugh
2. you didn't provide any information regarding the version of mekanism and forge, so we can't tell you if it's already fixed or it's a new bug

Apologies. My first time logging an issue.
Mekanism Versions:
Mekanism-1.16.4-10.0.17.444.jar
MekanismAdditions-1.16.4-10.0.17.444.jar
MekanismGenerators-1.16.4-10.0.17.444.jar
MekanismTools-1.16.4-10.0.17.444.jar

Forge Version:
forge-34.1.42

Currently playing in Valhelsia 3 Modpack pre5-3.1.0 .

My idea would have some sort of filtered entity detector that would emit a redstone signal to your reactor for any endermen nearby I'm not sure if Dark Utilities mod has any way or form thats similar