Thanks for the replies everyone, looks like this is just a flaw of the h90 we have to live with. The insert loops are simply not usable. Perhaps the technology will improve in time but for now I’m going to be running my overdrive before the h90. If I need to use modulation effects pre overdrive I’ll have to swap some cables around… not ideal.
It’s disappointing because one of the major selling points for me was the convenience of the routing. The h90 can still co-exist with my analogue gear, it’s just not as seamless as advertised.
