Check the well known forums for user feedback on the S4R box: Here (obviously)., DigitalSpy, and AVForums at least. For a new box it appears pretty stable from what I've read.
Note the T4R is crippled to two tuners only on Freeview and there are far fewer channels in HD cf Freesat.
Once the TV confirms the LNB still works, if two tuners is enough, possibly seek out an old Humax Foxsat-HDR and install the custom firmware / patch on it...

You may seldom need to record more than two channels and could use the EE box for those occasions; or even the TV with an attached usb hard drive.
Picture quality / appearance may well be due to
per input settings differences... so internal tuner uses one set, internal streamer another, and the hdmi input from the EE box a third... Tweaking / copying settings is
usually simple enough.
Note that the EE box may also do a worse job of upscaling cf the TV so try that as well.
Your eyeballs are what matters. So set things to suit you!
UHD HDR content from external sources sometimes need specific hdmi inputs to be used and enabled to work... it's not always automatic and can be called different things by different makers.