latextools .sublime-project texroot does identify a texroot

I am attempting to build a latex project with included files using LatexTools in sublime text 3. I cannot build a pdf from a subfile. Please tell me how to set up a sublime project to enable pdf building by using ctrl+b while having the editor opened on a child tex file.

Below is a minimal example:

qsar_catalogue.tex:

\documentclass{article}
\title{Exploratory review of QSARs in Toxicology}
\begin{document}
\include{sections/3_methods}
\end{document}


sections/3_methods:

\section{Methods}
test


This stack exchange question mentions that a root tex file can be created by putting the below in your .sublime-project file:

 { "settings": { "TEXroot": "./yourfilename.tex" } } 

This should enable tex building from tex files that are included via a \include command. I believe I have done this correctly. If I run check system I get the below key/field:

TeX Root
--------
/home/my_user/path/to/qsar_catalogue.tex


However when I try to build from /home/my_user/path/to/sections/3_methods.tex I get:

entering extended mode
(/home/my_user/path/to/sections/methods.tex
LaTeX2e <2016/02/01>
Babel <3.9q> and hyphenation patterns for 81 language(s) loaded.
! Undefined control sequence.
l.1 \section
{Methods}
?


I found more instructions at latextools documentation but after a few hours of changing various settings I had no luck.

• That does not look like the output from the LaTeXTools build system. Can you try to press ctrl+shift+b and select LaTeX. In addition you can try to check your builder settings in the file Preferences > Package Settings > LaTeXTools > Settings - User Jul 11, 2017 at 21:28