ODEProblem error --> LoadError: UndefVarError: _derivative not defined

I am getting an error when solving a system of differential equations. I have made the below example to demonstrate.
Julia v1.5.3
ModelingToolkit v5.6.0
OrdinaryDiffEq v5.50.2

using ModelingToolkit, OrdinaryDiffEq, Plots

@variables V_n1 V_n2 V_n_mid
@parameters t
D = Differential(t)

eqs = [ 0 ~ 5.0e-5((D(V_n2)) - (D(V_n_mid)))
        0 ~ 1.0e-5((D(V_n_mid)) - (D(V_n1))) + 5.0e-5((D(V_n_mid)) - (D(V_n2)))
        0 ~ V_n1 - 0.5 - (sin(80t))]

vars = [V_n1, V_n2, V_n_mid]
params = []

sys = ODESystem(eqs, t, vars, params)
u0 = zeros(length(eqs))
du0 = zeros(length(eqs))
tspan = (0.0,100.0)

prob = ODEProblem(sys,u0,tspan,params)
sol = solve(prob, Trapezoid())

The error occurs at the solve step and gives message:

ERROR: LoadError: UndefVarError: _derivative not defined
 [1] macro expansion at /Users/user/.julia/packages/ModelingToolkit/JtDFb/src/build_function.jl:476 [inlined]
 [2] macro expansion at /Users/user/.julia/packages/RuntimeGeneratedFunctions/tNQoo/src/RuntimeGeneratedFunctions.jl:95 [inlined]
 [3] macro expansion at ./none:0 [inlined]
 [4] generated_callfunc at ./none:0 [inlined]
 [5] (::RuntimeGeneratedFunctions.
 --------  [Very long message] -------- 

I think I need to use:

prob = DAEProblem(sys, du0, u0, tspan, differential_vars=[true,true,false])

But there is no DAESystem equivalent to ODESystem.
Thanks for the help.

Hey Grant, we are working on general transformations for DAEs in StructuralTransformations.jl. It’s free for academic use. Currently, it only handles the case where the derivative variables on the LHS. I am working on handling the general case along with a singularity-removing alias elimination algorithm.

This is currently in development. As @YingboMa notes, the solution is in StructuralTransformations.jl.