Sadly I cannot create a reproducible example from my code, writing the problem to file and reading it resolves the problem.
I now use JuMP.set_attribute(model, MOA.LexicographicAllPermutations(), false) and that solves very quickly. It makes sense that it took very long before if it was going through all 10! objective permutations for the problematic model, I’m only interested in the specific order of the objectives that I provide.