\mathsf{} creates a black square in SIAM's latex template see code below. (replace contents of ex_article.tex file with text below leave other SIAM files alone) I've narrowed it down to this only happens if the \mathsf is preceded and followed by open and close parentheses in math mode and a period in non-math mode and only if the expression hugs the end of a line.
It's not caused by the lack of sections, the abstract etc I've omitted those merely to make the example shorter.
\documentclass[review,onefignum,onetabnum]{siamart190516}
\usepackage{algorithmic}
\usepackage{amssymb}
\usepackage{adpwrapfig}
\usepackage{caption}
%%\usepackage{amsthm}
\headers{An Example Article}{D. Doe, P. T. Frank, and J. E. Smith}
\begin{document}
adfsadf asdfs asffaf adsf as sad fd f asdf vad adf adsf afsad ds fasfd saf d $(1) \mathsf{abc}(1,2) $.
adfsadf asdfs adsf as sad fd f asdf vad adf adsf afsad ds fasfd saf d $(1) \mathsf{abc}(1,2) $.
\end{document}
siamart171218notsiamart190516; also I don't know what theadwrapfigpackage is; I don't think it's standard. Makes it hard to test your code. (Though I did and will post an answer in a second.) – frabjous Apr 09 '22 at 01:51