LaTex nested description list - item label placement error - is it required to follow \end{description} with blank line, \par, \mbox{} or \item[]?

Question

Is it a requirement to follow a nested \end{description} with a blank line, \par, \mbox{} or \item[] in a LaTex nested description list? None of the documentation or samples I have reviewed suggests it is, but I have a layout error.

Using LaTex, my nested description list results in the labels of the item following the end of an inner description list being wrongly placed, often over-printed on the next item's label. I can resolve this by following the existing \end{description} with a newly inserted trailing blank line, \par, \mbox{}, or \item[]. Adding a blank line or \par produces the best results. Following David's answer below, I know that deleting the unneccessary \par commands also resolves the error. This blank line or \par solution works for me, seems logical and does not disrupt any non-nested list either, but why are any changes required? Am I missing something or is a bug?

Here are a couple of samples of the errors:

Here are the corresponding diff's to fix the error - simple insertion of a trailing \par following the \end{description}:

@@ -865,5 +865,5 @@
  a text which ... grammar  \par
-\end{description}
+\end{description}\par
 \item[{(J002)}]\par
  Acronyms and abbreviations  \par

@@ -980,5 +980,5 @@
  a computer ...
-\end{description}
+\end{description}\par
 \item[{(J004)}]\par
  Trademarks are ...  \par

Here is a tiny.tex file which exhibits the same layout errors (I have tried to keep the blank lines and \par placed as in the original tex file):

\documentclass[12pt,twoside]{book}\makeatletter
\makeatother
\begin{document}
\chapter[{    DETAILED DESCRIPTION ...  }]{    DETAILED DESCRIPTION ...  }\par
 \begin{description}
\item[{(J001)}]\par
 Definitions  \par
  \begin{description}
\item[{(post-verification ...)}]\par
 a text ...  \par
\end{description}
\item[{(J002)}]\par
 Acronyms and abbreviations  \par
  \begin{description}
\item[{(ECMA)}]\par
 European ...  \par
\item[{(YACC)}]\par
 Yet Another Compiler Compiler  \par
\end{description}
\item[{(J003)}]\par
 Glossary  \par
  \begin{description}
\item[{(2-tuple)}]\par
 a tuple with two ordered elements, an ordered pair  \par
\item[{(yacc)}]\par
 a computer utility program which will
\end{description}
\item[{(J004)}]\par
 Trademarks are identified ...  \par
\item[{(J005)}]\par
The following terms are ...:  \par
  \begin{description}
\item[{(+)}]\par
 (+)
\end{description}
\end{description}    CLA ...  \par
\end{document}

And here is the resulting PDF snippet cut from the pdflatex output and showing the same errors as above:

If I insert the \traceparagraphs1 command and insert a single blank line after the \end{description} command and diff the log output I see the following differences which I do not understand but may explain why the blank line is needed to produce the correct format. First we add a blank line:

--- tiny5.tex   2020-12-18 19:37:23.966114635 +0000
+++ tiny6.tex   2020-12-18 19:37:38.690148323 +0000
@@ -17,4 +17,5 @@
\end{description}



\item[{(J002)}]\par
  Acronyms and abbreviations  \par

The we apply the diff utility to the tex log files:

--- tiny5.log   2020-12-18 19:37:58.370193342 +0000
+++ tiny6.log   2020-12-18 19:38:02.762203391 +0000
@@ -1,8 +1,8 @@
-This is pdfTeX, Version 3.14159265-2.6-1.40.21 (TeX Live 2020) (preloaded format=pdflatex 2020.12.13)  18 DEC 2020 19:37
+This is pdfTeX, Version 3.14159265-2.6-1.40.21 (TeX Live 2020) (preloaded format=pdflatex 2020.12.13)  18 DEC 2020 19:38
@@ other diffs omitted here as mostly tiny5 to tiny6 filename changes @@
@@ -113,9 +113,4 @@
@firstpass
-[]
-@\par via @@0 b=0 p=-10000 d=100
-@@1: line 1.2- t=100 -> @@0



-@firstpass
 []\OT1/cmr/m/n/12 The following terms are ...:
 @\par via @@0 b=0 p=-10000 d=100

Any clues appreciated.

Answer 1

It is not clear why you had all the \par I started by deleting them all, then I think got the output you intended.

\documentclass[12pt,twoside]{book}\makeatletter
\makeatother
\begin{document}
\chapter[{    DETAILED DESCRIPTION ...  }]{    DETAILED DESCRIPTION ...  }
 \begin{description}
\item[{(J001)}]
 Definitions

  \begin{description}
\item[{(post-verification ...)}]
 a text ...
\end{description}
\item[{(J002)}]
 Acronyms and abbreviations

  \begin{description}
\item[{(ECMA)}]
 European ...
\item[{(YACC)}]
 Yet Another Compiler Compiler
\end{description}
\item[{(J003)}]
 Glossary

  \begin{description}
\item[{(2-tuple)}]
 a tuple with two ordered elements, an ordered pair
\item[{(yacc)}]
 a computer utility program which will
\end{description}
\item[{(J004)}]
 Trademarks are identified ...
\item[{(J005)}]
The following terms are ...:

  \begin{description}
\item[{(+)}]
 (+)
\end{description}
\end{description}    CLA ...
\end{document}