Question: solving ODE system which has piecewise?

Hello all,

I have an ODE system called RedSys which is below and incons1 which is its initial condition.

When I want to solve this system by dsolve numeric with this command:

dsolve((convert(RedSys, set)union incons1), numeric, implicit = true);

I face an error which says :

system should be linear in leading derivative. However when check I do not see any non linearity.

could you please let me know what should I do to solve this system by dsolve/numeric?

Thanks so much,

RedSys := [10*diff(X21(t),t)+diff(X97(t),t) = piecewise(t < 0,0,.2e-2), -1.*
diff(X97(t),t)-800.0100000*diff(diff(X97(t),t),t)-25.00000000*diff(X63(t),t)+
25.00000000*diff(X74(t),t)-1.*piecewise(t < 25,0,-1) = piecewise(t < 20,0,
piecewise(t < 25,1/5*t-4,1)), diff(X16(t),t) = 100*diff(X21(t),t)-10*X16(t), .\
4106328774e-7*diff(diff(X63(t),t),t)-.6056424308e-7*diff(diff(diff(X74(t),t),t
),t)-.2204071969e-5*diff(diff(X74(t),t),t)+.1466545990e-5*diff(X63(t),t)-.\
1207945460e-3*diff(X74(t),t)-10*diff(X21(t),t)-X21(t) = 100*diff(X21(t),t)-10*
X16(t), 2500.000000*diff(X63(t),t)-2500.000000*diff(X74(t),t) = piecewise(.\
1500000000e-1 < X97(t)-.4000000000e-3*X63(t),100000.*X97(t)-40.00000000*X63(t)
-1500.000000+10000*diff(X97(t),t)-.1000000000e-8*diff(diff(X74(t),t),t)-4.0000\
00000*diff(X63(t),t),piecewise(X97(t)-.4000000000e-3*X63(t) < -.1500000000e-1,
100000.*X97(t)-40.00000000*X63(t)+1500.000000+10000*diff(X97(t),t)-.1000000000\
e-8*diff(diff(X74(t),t),t)-4.000000000*diff(X63(t),t),0))];

incons1 := {X16(0) = 0, X21(0) = 0, X63(0) = 0, X74(0) = 0, X97(0) = 0, D(X16)
(0) = 0, D(X21)(0) = 0, D(X63)(0) = 0, D(X74)(0) = 0, D(X97)(0) = 0};