What is going on?

images are in chronological order

So I’ve recently switched from nest to an ecobee premium. I’ve been having issues. As shown in the images the device seems to reach desired temp, shut off, restart, calibrate and then appear at a higher temp. After a minute or so the temp would drop and the heating would begin again. Aside from that there’s issues with the ecobee calling for heat very often.

Also, it’s important to know that I’ve gotten Nest error code: E74 a couple of times while the heating is still on. It’s also important to note that I had the flame sensor cleaned and filter replaced I have an old Magic-Pak system.

Any advice or suggestions would be really appreciated. Thank you