Question: Problem with division by zero

hi.i encounter with another error for solving couple equations.

bcs := {f1(0) = 0, f1(L) = 0, f2(0) = 0, f2(L) = 0, f3(0) = 0, f3(L) = 0, ((D@@1)(f2))(0) = 0, ((D@@1)(f2))(L) = 0, ((D@@1)(f3))(0) = 0, ((D@@1)(f3))(L) = 0}; sys := subs(omega^2 = omega2, {PDE[111], PDE[222], PDE[333]}); sys2 := PDEtools:-dchange({x = L*y, f1(x) = g1(y), f2(x) = g2(y), f3(x) = g3(y)}, sys, [g1, g2, g3, y]); indets(sys2, specfunc(diff)); solve(sys2, {diff(g3(y), `$`(y, 4)), diff(g1(y), y, y, y), diff(g2(y), y, y, y, y)}); sys3 := subs(omega2 = 10^19*omega3, sys2); bcs3 := {g1(0) = 0, g1(1) = 0, g2(0) = 0, g2(1) = 0, g3(0) = 0, g3(1) = 0, ((D@@1)(g2))(0) = 0, ((D@@1)(g2))(1) = 0, ((D@@1)(g3))(0) = 0, ((D@@1)(g3))(1) = 0}; extra_bcs := `minus`({seq(seq(((D@@i)(g1))(a), i = 0 .. 1), a = 0 .. 1), seq(seq(((D@@i)(g2))(a), i = 0 .. 1), a = 0 .. 1), seq(seq(((D@@i)(g3))(a), i = 0 .. 3), a = 0 .. 1)}, `~`[lhs](bcs3)); dsys4 := {bcs3, sys3}; ds := dsys4[1]; indets(dsys4[1], specfunc(diff)); solve(dsys4[1], {diff(g3(y), `$`(y, 4)), diff(g1(y), y, y, y), diff(g2(y), y, y, y, y)}); newsys := {ds[2], ds[3], diff(ds[1], y)}; indets(newsys, specfunc(diff)); S := solve(newsys, {diff(g1(y), `$`(y, 3)), diff(g2(y), `$`(y, 4)), diff(g3(y), `$`(y, 4))}); nops(%); bcs2 := eval[recurse](convert(ds[1], D), `union`({y = 0}, bcs3)); nops(`union`(bcs3, {bcs2}));

Error, (in simpl/eval) numeric exception: division by zero

division_by_zero.mw

please help.thanks..