Hello Hans,

I'm sorry but when you were adding my sorting rules for Czech, you've (probably by accident) deleted the definition of \czsortdivisionch which leads to errors when trying to sort a word on "ch".
I've also made some minor corrections. Here is the updated version:

% ---
\def\czsortdivisionch{ch}
\def\czsortdivisionCh{Ch}

\startmode[sortorder-cz]
    \exportsortexpansion {aacute} {a+1}
    \exportsortexpansion {Aacute} {A+1}
    \exportsortexpansion {ccaron} {c+1}
    \exportsortexpansion {Ccaron} {C+1}
    \exportsortdivision  {c+1}    {ccaron}
    \exportsortexpansion {dcaron} {d+1}
    \exportsortexpansion {Dcaron} {D+1}
    \exportsortdivision  {d+1}    {dcaron}
    \exportsortexpansion {eacute} {e+1}
    \exportsortexpansion {Eacute} {E+1}
    \exportsortexpansion {ecaron} {e+2}
    \exportsortexpansion {Ecaron} {E+2}
    \exportsortreduction {ch}     {h+1}
    \exportsortexpansion {ch}     {h+1}
    \exportsortreduction {Ch}     {H+1}
    \exportsortexpansion {Ch}     {H+1}
    \exportsortdivision  {h+1}    {czsortdivisionch}
    \exportsortexpansion {iacute} {i+1}
    \exportsortexpansion {Iacute} {I+1}
    \exportsortexpansion {ncaron} {n+1}
    \exportsortexpansion {Ncaron} {N+1}
    \exportsortdivision  {n+1}    {ncaron}
    \exportsortexpansion {oacute} {o+1}
    \exportsortexpansion {Oacute} {O+1}
    \exportsortexpansion {rcaron} {r+1}
    \exportsortexpansion {Rcaron} {R+1}
    \exportsortdivision  {r+1}    {rcaron}
    \exportsortexpansion {scaron} {s+1}
    \exportsortexpansion {Scaron} {S+1}
    \exportsortdivision  {s+1}    {scaron}
    \exportsortexpansion {tcaron} {t+1}
    \exportsortexpansion {Tcaron} {T+1}
    \exportsortdivision  {t+1}    {tcaron}
    \exportsortexpansion {uacute} {u+1}
    \exportsortexpansion {Uacute} {U+1}
    \exportsortexpansion {uring}  {u+2}
    \exportsortexpansion {Uring}  {U+2}
    \exportsortexpansion {yacute} {y+1}
    \exportsortexpansion {Yacute} {Y+1}
    \exportsortexpansion {zcaron} {z+1}
    \exportsortexpansion {Zcaron} {Z+1}
    \exportsortdivision  {z+1}    {zcaron}
\stopmode
% ---