US Blu-Ray discs on my player have poorer picture quality than UK ones - why?

[mojo_navigator]

Hi Everyone,

Hope I can solicit some advice on solving an intractable problem that I have

I live in the UK and I have a multi-region player

The player is a Sony BDP-S7200 that I bought from http://www.mrmdvd.com/ who perform multi-region hacks on these items prior to sale

I have noticed that the picture quality on US blu-ray discs is often substantially poorer than with UK discs

For example, areas that should display film grain instead display noise in a strong and distracting way

Criterion’s tend to be particularly bad so obviously something is not right

To remedy this, I'm contemplating ordering an Oppo BDP-103 from the US but am concerned that this may not fix my problem

Does anyone have any idea why this issue might be occurring?

Could it be that in the manual process that mrmdvd performed to make the player multi-region that this issue could have been introduced? (I have owned a different Sony player from mrmdvd previously that also exhibited this problem)

Is it possible that the multi-region conversion perfomed by Oppo might have been done differently?

Or is there some kind of US/UK incompatibility (either voltage or 50z/60hz) that could be causing this?

Would appreciate input from those with technical experience as to how this all works

Thanks in advance