longtable/exam: longtable doesn't page-break inside the solution environment

it doesn't seem related to longtable, a simple solution of

aaa

pagebreak

bbb

the page break is similarly ignored. The solution is set in a box and it seems the class does not always unbox it to allow page breaks.

As a pointer to a possible solution this version (just added a vspace) breaks but has a probably unwanted long white block at the end.

documentclass[answers]{exam} 
usepackage{longtable}
newboxmybox
usepackage{caption,booktabs,siunitx,multicol}
begin{document}
setboxmyboxvbox{
}

    begin{questions}
        question some question
        begin{solution}
            setlengthLTleft{0pt}
            setlengthLTright{0pt}
            begin{longtable}{
                    @{extracolsep{fill}}
                    lr
                    *{2}{%
                        S[table-format=2.2,
                        round-precision=2,round-mode=places,
                        round-integer-to-decimal=true]%
                    }@{}}
                toprule
                multicolumn{2}{c}{H1 and H2} & H3 & H4 
                midruleendhead
                left & right & 78.79 & 23.45 
                newpage
                left & right & 78.79 & 23.45 
                bottomrule
            end{longtable}


vspace{textheight}
        end{solution}
    end{questions}
end{document}

Note if you use longtable in a box you can usually get breaking to work but the head and foot will never be added so the lack of a table head on the second page is expected here (and not really fixable using longtable)