"Misplaced cr." and "Illegal parameter number in definition of reserved@a." errors in xtabular?

Trying to submit a paper to arXiv- the overleaf compiles fine, but the arXiv submissions shows two errors which halt compilation (these show up in the overleaf as well, but it compiles fine there).

The errors relate to a long table (xtabular), for submission with MNRAS style files. Any clues as to how I can fix the issues? The exact errors are:

Error 1:

Misplaced cr.

reserved@c ->ifnum 0=`{fi }cr 
                                  
l.567 ...textwidth}{l@{extracolsep{fill}}cccccc}

                                              
I can't figure out why you would want to use a tab mark
or cr or span just now. If something like a right brace
up above has ended a previous alignment prematurely,
you're probably due for more error messages, and you
might try typing `S' now just to see what is salvageable.

Error 2:

Illegal parameter number in definition of reserved@a.

<to be read again> 
                   1
l.567 ...textwidth}{l@{extracolsep{fill}}cccccc}
                                                  
You meant to type ## instead of #, right?
Or maybe a } was forgotten somewhere earlier, and things
are all screwed up? I'm going to assume that you meant ##.

The table is of the form:

onecolumn

centering

begin{xtabular*}{.85textwidth}{l@{extracolsep{fill}}cccccc}

hline

textbf{Column1} & textbf{Column2} & textbf{Column3} & textbf{Column4} & textbf{Column5} & textbf{Column6} & textbf{Column7}  hline

.....


label{tab:distance-table}

end{xtabular*}

% Don't change these lines

bsp    % typesetting comment

label{lastpage}

end{document}