`soul` and `soulpos` cause page restart if used heavily

Question

I use lots of highlights as it is used to mark my revision from each version before I gave to my lecturer. When I highlight lots of texts, I found out that sometimes page restarted in the middle.

After an hour of stress, I found the cause, that is heavy use of highlight as mentioned here. That page mention soul, but I use soulpos. It seems that both packages got the same bug.

Below is my code to make the highlight:

\usepackage{soulpos}
\ulposdef{\hly}{%
  \mbox{%
    \color{yellow}%
    \rule[-.8ex]{\ulwidth}{11pt}%
    \tolerance=1%
    \emergencystretch=\maxdimen}}

Any solution? Why this is happening? Can this kind of bug be fixed? Thanks.

EDIT:

From the comment section, this bug for soul is discussed and solved here. Sadly, soulpos did not use \countdef and the same fix can't be used.

EDIT after more testing:

Okay, now I become more confused:

1. With separate cls, soulpos did not get this problem. See here
2. With no separate cls, soulpos can't solve even with the minus. See here

This (No 2) got wrong page numbering, but not if I use .cls (see No 1)

\documentclass{article}
\usepackage{soulpos}

\makeatletter
\newcount\SOUL@minus
% \newcount\SOULPOS@minus
\makeatother

\usepackage{xcolor}
\usepackage{blindtext}

\ulposdef{\hly}{%
  \mbox{%
    \color{yellow}%
    \rule[-.8ex]{\ulwidth}{11pt}%
    \tolerance=1%
    \emergencystretch=\maxdimen}}
 
\begin{document}

\Blindtext[4]
\blindtext
\hl{Closing words

New paragraph!}

\clearpage

\Blindtext[4]
\blindtext
\hly{Closing words

New paragraph!}

\end{document}

Answer 1

After some trial and error, based on @quark67 comment, I found out that using this combo solve my issue. I haven't fully tested it, but it works for now.

\usepackage{soulpos}
\newcount\SOUL@minus

EDIT after more testing:

Okay, now I become more confused:

1. With separate cls, soulpos did not get this problem. See here
2. With no separate cls, soulpos can't solve even with the minus. See here