p_elem->root != this ' is true

[ianscottcamp]

I have been getting this error for a while now, since v2.1 and have since migrated to 3.0 and the problem has worsened. The debug console gets flooded with

ERROR: remove: Condition ' p_elem->_root != this ' is true.
At: core/self_list.h:77"

This seems to happen when I try to add_child or manipulate nodes in the current scene tree from a thread. This was not so much an issue before as the project would continue running despite this error, it would only start to lag as this error piled up on the console which I could completely avoid in the executable version of the project if i turn off debuging window. However lately I get random crashes with an additional error even in the executable as follows,

Nothing read: No such file or directory
ERROR: read: Server disconnected!
At: drivers/windows/stream_peer_tcp_winsock.cpp:203

Godot version: 3.0.3 x64

OS/device including version: windows7

Issue description: flood error "remove:condition ' p_elem->_root != this ' is true. At: core/self_list.h:77"

Steps to reproduce: add_child or manipulate nodes in scene tree from a thread

[ianscottcamp]

Solved. Using call_deferred on add_child function in the thread fixed this issue.