Some information

Operating system: Windows10 Version1909 Build 18363.752
Java version: 1.8.0_51 64bit
Minecraft version: 1.12.2-forge1.12.2-14.23.5.2768
Baritone version: 1.2.13
Forge mods (if used):

• OptiFine HD Ultra F5,
• Advanced Macros 7.7.7 (Source)

Exception, error or logs

java.lang.IllegalStateException, latest_barifail.log

How to reproduce

Create new world with seed 13.
Do #mine sand and #goto sand.
Baritone will throw execption java.lang.IllegalStateException
baritone.api.command.exception.CommandUnhandledException:
Mining will be aborted. Goto will work, but throws anyway.
Selection command family is unaffected by this bug.

For any others who find this issue: Use runOnMC( say, "#command" ) in macros instead.
It got implemented in newst versions of AM. Also fix for regular chat will happen too.

Try uninstalling advanced macros, that should fix the issue.

Gotta rebuild Baritone myself then. Thank you. :/

Found the bug...
Baritone forces to run itself onto main Minecraft thread.
Fixed this by putting Baritone iteraction in "sheduled task".
Also suggested AM devs to move chat back onto MC thread.

Minecraft is not thread safe. This is a AM issue