I'm trying to place string next to cactus and the printer just sits there trying to place but it fails and keeps trying. Is there a way to fix this? I'm looking at Extra air block settings but Im not sure if that's it.

Can you specify which versions of Minecraft, Forge, and Schematica you are using?

Additionally, attached is the scematic I am using

Version numbers
Minecraft 1.8
Forge Mod loader 8.0.99.99
Minecraft Forge 11.14.4.1577
LunatriusCore 1.1.2.30
Scematica 1.7.7.140

I don't know if we're still providing support for Minecraft 1.8; it's several years outdated.

My best guess is that this issue is MinecraftForge/MinecraftForge#3924, but I don't know when that actually started being a problem. (The actual summary of that issue is that tripwire stops working after relogging; it started out being very cryptic but was figured out later on). If you want a fix to that, you'll need to update to 1.12 at minimum. To be clear, I'm not sure if that's actually the issue causing that; it's only my guess.

Silly question, have you tried placing the string yourself?

Also, no updates/bugfixes for 1.8 anymore.