Is this my error or of pdfLaTeX?

[mail at heinzebert.de]

To Whom it may concern at texhax at tug.org
According to this E-Mail:
Sehr geehrter Herr Ebert —
mail at heinzebert.de wrote:
> To Whom it may concern
> The caption part of following statements generates several error  
> messages by using pdfLaTeX:
As the errors come from pdfLaTeX and not from TeXworks, this list  
(which is devoted solely to matters concerning TeXworks) is not the  
optimal place to ask.  I would suggest that you re-send your question  
to texhax at tug.org.
Mit freundlichen Grüßen —
Philip Taylor

TeXworks 2019 version 0.6.3(travis-ci) [r.a2470ca, 16.03.2019 18:06]
Windows 8 professional 64Bit version
The caption part of following statements generates several error  
messages by using pdfLaTeX:

\begin{figure}[htbp]
    \centering
    \includegraphics[scale=0.5]{CollatzTree.pdf}
    \caption{Grid graph representation of the tree  
${\boldsymbol{A}}_{\overrightarrow{C}}(1)$. The map  
$\overrightarrow{C}$ is the generating function.}
    \label{fig:FT}
\end{figure}

But after skipping every message by entering 'return' the desired  
output of the caption is achieved.
You can test the example.tex in the appendix and see that this happens  
for \section too.

Furthermore the same statements generate a overwhelming lot of error  
messages if I want to submit an article to the arXiv-Server. There  
even \subsection with mathematical notations as above generates about  
50 lines of error messages.

With many thanks for your efforts and kind regards
Heinz Ebert
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