I am not sure you did anything wrong, but a lot of compilation heuristics changed between 1.5 and 1.6. Sometimes this means that you can get the same result with much simpler code, but occasionally it means that if your code relied on the compiler trying inference very hard it will give up sooner.
In any case, the first thing I would do is investigate with the standard tools (@code_warntype, BenchmarkTools.@btime), narrow down the problem to specific parts with packages like
and then look at the generated code. If you narrow down the problem to something specific, you are more likely to get a suggestion about it here.