Your screen shot looked like it may have been displaying metadata that could have been embedded by the ripping program. It was just a thought. Also as long as you have iCloud sync turned on Infuse should keep the correction if you can find the correct series with an edit.
Also I don’t think you need the year for the TV show. I believe that if you name the files “The Avengers S01E01.mkv” they would automatically find the correct metadata. I’m not where I can check right now but it looks like the year isn’t necessary and may be causing the initial problem with a TV series.
I don’t know about makemkv but Infuse will often determine if a video is a TV show and will search thetvdb by looking for the S0xE0x immediately after the show title while it will usually look in the movie database when a numerical year follows the title. Only a small minority of TV shows will require a numerical year after the series name and before the S0xE0x section.
Note, this is just my experience over the last few years.