Playback switching to 1080i

Hi,
I noticed recently (few months back), that playback from rasplex is switching to 1080i for some reason. I still have same TV i had when i did not occurred. I do have adjust refresh rate on, so i do get 24p playback. Which works after restart of rPI and usually for few days. Then i starts playback on 1080i.
Do you think what could cause it on resPlex side? I updated TV firmware, so it also maybe that.