Using 1.16.5, latest versions of IR, UMC and TrackAPI, latest version of Java 8 - this applies to both client and server, and the issue is also present in singleplayer.

When the casting basin is placed down either in survival with the appropriate blocks in the inventory, or creative mode, only the tower part is placed. The basin itself doesn't appear or even list its components (the stone bricks and sand) in the required ingredients when attempting to place with ingredients missing. The basin does not show up in the ghost preview either when deciding where to place the structure.

Similarly with the steam hammer its base with steel block is also missing and does not show in the requirements.

If you attempt to place the relevant blocks that are missing manually, they are not recognised as part of the structure when you "complete" it using the IR wrench.

When either structure is completed, the blocks that are still recognised all disappear but retain their collisions, and a generic shadow appears on the ground - no model or anything shows up in their place, and the multiblock structure doesn't function.

The other multiblock structures are unaffected.

I've noticed many repeats of the following in the logs on both the client side and server side:
[Worker-ResourceReload-13/WARN]: Multiblock CASTING is missing support for sand
[Worker-ResourceReload-13/WARN]: Multiblock CASTING is missing support for brickStone
[Worker-ResourceReload-6/WARN]: Multiblock STEAM_HAMMER is missing support for blockIron

And on the server side only, many repeats of the following:
[Server thread/WARN]: Multiblock TE is null: (21, 71, 169) (1, 0, 14) false class cam72cam.immersiverailroading.multiblock.CastingMultiblock$CastingInstance

Unsure if it's down to a mod conflict or not - I've already established a separate conflict with The One Probe which causes major rendering problems when near stock placed on rails and removed that mod from the equation for that reason.

That's definitely a mod conflict, can't do much without a full log and/or mod list.

Sorry to say I had neglected to add that myself and several other players tested this on a setup with just Forge and IR only, no other mods, and the issue was still the same.

I'm experiencing the same issue on 1.16.5

My mod list:
Immersive Engineering 1.16.5-5.1.0-148
Immersive Railroading 1.16.5-forge-1.10.0
jei 1.16.5-7.8.0.1009
journeymap 1.16.5-5.8.5p6
TrackAPI 1.16.4-forge-1.2.1
UniversalModCore 1.16.5-forge-1.2.1

Log:
latest.log

Thanks

your log doesnt mention anything with the basins, did you accidently upload an old one

The log was from when I was playing around with more things from Immersive Engineering and Immersive Railroading.

I will create a log with just trying to place the basin when I'm back later.

ive had the same issue ill try catch one as well

I think the multiblock in question is just called CASTING. Not sure if the basin part would be mentioned explicitly.

Just created a new superflat creative world, tried to place just the casting multiblock. It also doesn't show the basin portion in the blueprint:

After placing it down, it just shows the smelting tower, as mentioned:

This times log:
latest.log

Forgot one thing: Loaded it again, hit it with the wrench, it got replaced by just a big shadow. The hitbox still seems to be there.

Logged nothing.

Left the poor chicken kind of confused ;-)

Experiencing same issue on 1.16.5 w/JEI, TrackAPI, UniversalModCore, IE, IR, and JourneyMap.

Likewise, all the photos above express my same frustrations with 1.10.0 regarding its failure to render the casting basin, and my list of mods only consists of Immersive Railroading, Track API, Universal Mod Core and Immersive Engineering. I'm using the latest editions for each mod regarding 1.16.5 and yet IR has continuously failed, even after multiple reinstallations and computer factory resets.

Reinstalling won't help since it's a bug in IR's code. Will hopefully get fixed soon as Cam has gotten back to coding