Thanks for looking at that further.

Re: the second issue, the problem seems to start here, with this: <table style="float:left" width="100%"> element (see PROBLEM below), which

(a) seems out of place

(b) is never closed w/ "</table>, as best I can see (as per inspection of saved output from curl "https://www.gnu.org/software/emacs/manual/html_mono/flymake.html")

Instead, this "<table>" seems to be closed with a mismatched "</ul>"

          <p>Syntax checks happen &ldquo;on-the-fly&rdquo;.  Each check is started whenever:
          </p>

          <table style="float:left" width="100%">  <== PROBLEM?
            <li> <code>flymake-mode</code> is started, unless
              <code>flymake-start-on-flymake-mode</code> is <code>nil</code>;

            </li><li> the buffer is saved, unless <code>flymake-start-on-save-buffer</code> is
                   <code>nil</code>;

                 </li><li> some changes were made to the buffer more than <code>0.5</code> seconds ago
                                                                                           (the delay is configurable in <code>flymake-no-changes-timeout</code>).

                      </li><li> When the user invokes the command <code>flymake-start</code>.
                           </li></ul>  <== PROBLEM?

            <p>If the check detected errors or warnings, the respective buffer
               regions are highlighted.  See <a href="#Finding-diagnostics">Finding diagnostics</a>, for how to
                                                                                                   learn what the problems are.
            </p>

I am unfamiliar w/ Texinfo, but I nonetheless don't see any "obvious" reason that a <table> element should be emitted at the above location, based on the below excerpt from https://git.savannah.gnu.org/cgit/emacs.git/tree/doc/misc/flymake.texi?h=emacs-29#n115 (I'm just guessing on the corresponding version of this file currently used for the online documentation)

    Syntax checks happen ``on-the-fly''.  Each check is started whenever:

    @itemize @bullet
    @item
    @code{flymake-mode} is started, unless
    @code{flymake-start-on-flymake-mode} is @code{nil};

    @item
    the buffer is saved, unless @code{flymake-start-on-save-buffer} is
    @code{nil};

    @item
    some changes were made to the buffer more than @code{0.5} seconds ago
    (the delay is configurable in @code{flymake-no-changes-timeout}).

    @item
    When the user invokes the command @code{flymake-start}.
    @end itemize

Perhaps this is helpful; if not please pardon & ignore.