Peter,
I haven’t used the mx70 for a few years once we switched to the ATEM platform. However, a lot of issues that I ran across with component or any signal was that we had to run signals through a scan converter. We used a Sony 1024. This allowed us to recook the digital signal to one the mx70 could see and use. I actually only used component inputs for the DSK to provide a better lower third graphic for our uses. You also have to realize the mx70 is strictly 720x480i at 29.97. Unless your mx70 was the 1080 but do t quote me on that, we never had one.
If you need a very simple basic mixer for your t7 or t7i I’d recommend highly the ATEM mini. It’s 4 hdmi inputs, and has built in up/down crosses. Best part is it’s CHEAP like less than $1k. Rent one from someone like lensrentals.com and give it a try.
Best of luck!
Jim