Error with high order derivative with Flux.chain and DiffEqFlux.FastChain

using Flux, DiffEqFlux
using Diffractor: var"'", ∂⃖

chain = FastChain(FastDense(1,12,Flux.σ),FastDense(12,1),(x,p) ->x[1])
initθ = (DiffEqFlux.initial_params(chain))
chain_f = (x) -> chain([x], initθ)
chain_f(1.)
chain_f'(1.)
chain_f''(1.)
Internal error: encountered unexpected error in runtime:
BoundsError(a=Array{Any, (0,)}[], i=(1,))

chain = Flux.Chain(Dense(1,12,Flux.σ),Dense(12,1),(x) ->x[1])
chain([1.])
chain_f = (x) -> chain([x])
chain_f(1.)
chain_f'(1.)

chain_f''(1.)
ERROR: MethodError: no method matching +(::Tuple{ChainRulesCore.Tangent{ChainRules.var"#1201#1203"{Vector{Float64}, Tuple{ChainRulesCore.ProjectTo{Float64, NamedTuple{(), Tuple{}}}}}, NamedTuple{(:ȳ, :projects), Tuple{Vector{Float64}, Tuple{ChainRulesCore.ZeroTangent}}}}, ChainRulesCore.NoTangent})
Closest candidates are:
  +(::P, ::ChainRulesCore.Tangent{P}) where P at ~/.julia/packages/ChainRulesCore/7ZiwT/src/tangent_arithmetic.jl:133
  +(::Any, ::ChainRulesCore.AbstractThunk) at ~/.julia/packages/ChainRulesCore/7ZiwT/src/tangent_arithmetic.jl:123
  +(::Any, ::Union{InitialValues.NonspecificInitialValue, InitialValues.SpecificInitialValue{typeof(+)}}) at ~/.julia/packages/InitialValues/P5PLf/src/InitialValues.jl:160

  julia> versioninfo()
  Julia Version 1.7.0-rc3
  Commit 3348de4ea6 (2021-11-15 08:22 UTC)
  Platform Info:
    OS: macOS (x86_64-apple-darwin19.6.0)
    CPU: Intel(R) Core(TM) i5-1038NG7 CPU @ 2.00GHz
    WORD_SIZE: 64
    LIBM: libopenlibm
    LLVM: libLLVM-12.0.1 (ORCJIT, icelake-client)
  Environment:
    JULIA_NUM_THREADS = 4

Start by running the Julia 1.7.0-rc3 reproducer from the issue and compare the FastChain and Flux.Chain cases. Trace the second-derivative calls using the shown errors as the starting point; done means both examples compute the second derivative without the reported internal error or MethodError.