EnzymeVJP often fails is automatic sensealg determination

[ArnoStrouwen]

Deleting the sensealg keyword in e.g. this tutorial:
https://docs.sciml.ai/SciMLSensitivity/dev/examples/optimal_control/optimal_control/
gives the warning that EnzymeVJP does not work on the problem.
However, manually specifying Enzyme, e.g. InterpolatingAdjoint(autojacvec = EnzymeVJP), seems to work fine.
The vjp calculation thus differ in the two places?

A first weird thing I found was the use of du in duplicated.
https://github.com/SciML/SciMLSensitivity.jl/blob/master/src/concrete_solve.jl#L19

[ChrisRackauckas]

Is there an internal alias check? Try changing one of the du's to a copy and see if that fixes it. Other than that, I don't think there's a difference in the vjps, but there must be if that is failing

[ArnoStrouwen]

Already tried that before, did not work. I'll have to dive deeper into the code.