Thank you @ChrisRackauckas !
Done.
The problem was jac=true in the prob = ODAEProblem(simpsys, u0, tspan, params, jac=true)
Thank you @ChrisRackauckas !
Done.
The problem was jac=true in the prob = ODAEProblem(simpsys, u0, tspan, params, jac=true)