Error in getMetricsFromLatex(TeXMetrics, verbose = verbose) - r

Question

When compiling R code within a child, I get the following error.
Error in getMetricsFromLatex(TeXMetrics, verbose = verbose) :
TeX was unable to calculate metrics for the following string
or character:
m
Common reasons for failure include:
* The string contains a character which is special to LaTeX unless
escaped properly, such as % or $.
* The string makes use of LaTeX commands provided by a package and
the tikzDevice was not told to load the package.
The file worked flawlessly until I changed one tiny detail that I cannot recall. The tikzDictionary is in the directory of the first child containing R-code. I removed the tikZDictionary to no avail. The file created is empty (0 Bytes). Taking the code and compiling it in a file with the appropriate headers works fine. I tried copying the contents of the whole thesis to a new folder and recompile it there, but the same problems occur there.
> sessionInfo()
> R version 3.4.0 (2017-04-21) Platform: x86_64-apple-darwin16.5.0 (64-bit) Running under: macOS Sierra 10.12.4
>
> Matrix products: default BLAS:
> /System/Library/Frameworks/Accelerate.framework/Versions/A/Frameworks/vecLib.framework/Versions/A/libBLAS.dylib
> LAPACK:
> /System/Library/Frameworks/Accelerate.framework/Versions/A/Frameworks/vecLib.framework/Versions/A/libLAPACK.dylib
>
> locale: [1]
> en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8
>
> attached base packages: [1] stats graphics grDevices utils
> datasets methods base
>
> other attached packages: [1] tikzDevice_0.10-1 plyr_1.8.4
> xtable_1.8-2 knitr_1.15.1
>
> loaded via a namespace (and not attached): [1] compiler_3.4.0
> magrittr_1.5 tools_3.4.0 Rcpp_0.12.10 [5]
> codetools_0.2-15 filehash_2.4-1 stringi_1.1.5 highr_0.6
> [9] grid_3.4.0 digest_0.6.12 stringr_1.2.0 evaluate_0.10
Copying all relevant files to a new directory and trying to compile it throws the same error.
1) Can one try to force the tikZdevice to recalculate the metrics?!
2) Can I get the correct metrics from elsewhere?
Thank you so much for your help.
I got it to work after a total of about 6 hours. I put all the R-Code in the main file, it compiles flawlessly. The ´main-tikzDirectory´ is in the same directory as the ´main´.
However, it is about 1000 lines of R code (we're talking about the results party of my whole thesis...), which I would rather have in a separate file.
As soon as I place anything in a child I get the same error. Also, while the error had been thrown in the ´R´ console before and no tex file is produced, when using the minimal example below the error message is written to the tex-file.
I provide a minimal example:
\documentclass[10pt,a4paper]{book}
\usepackage{geometry} % Titelseite braucht eigene Margins.
%\usepackage[ngerman]{babel} % Trennungsregeln, Datumsangabe etc. in Deutsch
\usepackage[T1]{fontenc} % europäischer Zeichensatz (Sonderzeichen, etc.)
%\usepackage[bitstream-charter]{mathdesign} % Moderne, serifenbetonte und sachliche Schriftart
\usepackage[utf8]{inputenc} % utf8 Eingabezeichensatz
\usepackage{xstring} % Testen/Vergleichen von (Sub)Strings
\usepackage{totcount} % Zähle Seitenzahlen, Abbildungen etc.
\usepackage{siunitx} % SI Einheiten
\DeclareSIUnit{\molar}{M}
%\usepackage{natbib} % Naturwissenschaftliche Zitierungen
\usepackage[sorting=none, citestyle=nature, maxnames=99, minnames=99, backend=biber]{biblatex}
\addbibresource{bibliography/bibliography.bib}
\renewcommand*{\bibfont}{\small}
\usepackage[version=3]{mhchem} % chemische Summen- und Strukturformeln
\usepackage{eurosym} % Euro-Zeichen
\usepackage{hyperref} %
\usepackage[xindy,acronym,nonumberlist,nomain]{glossaries} % Abkürzung + Abkürzungsverzeichnis
\makeglossaries %
\usepackage{multicol}
% Grafiken
\usepackage{tikz}
\usepackage{epsfig}
\usepackage{graphics}
\usepackage{graphicx}
% Tabellen
\usepackage{booktabs}
\usepackage{tabularx}
\usepackage{tabu}
\usepackage{array}
\usepackage{rotating}
\usepackage{bigdelim}
\usepackage{multirow}
\usepackage{float}
\usepackage{colortbl}
\usepackage{xcolor}
\def\TReg{\textsuperscript{\textregistered}}
\def\TCop{\textsuperscript{\textcopyright}}
\def\TTra{\textsuperscript{\texttrademark}}
%% Nummerierung
\setcounter{secnumdepth}{4}
%% Eigene Makros
\input{config/config}
\input{macros/InOderAm}
\input{macros/HideIfZero}
\input{macros/citenumCounter}
\input{macros/totalfiguresCounter}
\input{macros/totalappendixCounter}
%% Floats erst ab 80% auf eigene Seite
\renewcommand{\floatpagefraction}{.8}%
%% Dokument
\begin{document}
%% Knitr-optionen
<<setup, echo = FALSE, results= 'hide', message = FALSE>>=
library(xtable)
library(plyr)
opts_chunk$set(fig.path='figure/graphics-', cache.path='cache/graphics-', fig.align='center', dev='tikz', external=TRUE, fig.width=5, fig.height=5, fig.show='hold', cache=TRUE, global.par=FALSE)
knit_hooks$set(par=function(before, options, envir){
if (before && options$fig.show!='none') par(mar=c(4,4,.1,.1),cex=1,cex.lab=.9,cex.axis=.9,mgp=c(2,.7,0),tcl=-.3)
}, crop=hook_pdfcrop)
#
<<results, child="content/main/results/results2.Rnw">>=
#
\end{document}
The child is located some folders below.
<<corruption>>=
plot(runif(100,0,1)^2)
#