Based on my own experience, if something is wrong in that particular setup, it's a cabling.
Sumic cables are in my (and a lot other)experience incosistent product; neither sample 8among the same model) does not sound same as other. It is somewhat a fortune what you are getting when paying - you may won, but you may be deply disspointed.
So, you should try something more consistent, like Nordost, Transparent and the similar.
I would not change anything before trying new wiring.
My 5c
Sumic cables are in my (and a lot other)experience incosistent product; neither sample 8among the same model) does not sound same as other. It is somewhat a fortune what you are getting when paying - you may won, but you may be deply disspointed.
So, you should try something more consistent, like Nordost, Transparent and the similar.
I would not change anything before trying new wiring.
My 5c