+1 for earthing. I recently repositioned and tightened up my battery terminals and earthing points for the same reasons as you (dimming lights, idle hunting etc) and noticed a big improvement straight away. You might, like me, even consider upgrading to 2 or 0ga battery cables.
I'm not familiar with R32 mechanical HICAS but I had issues similar to you on my R33 and ended up locking it out. I'm sure it is a good system when it's working well but I could be fcked with it.