In the attached video, I first turn off the daylight cycle. Then I demonstrate that time can still be changed from day to night with command blocks. After that, when I try to repeat the process with the “Time” button in the chat/command window, it instead gets locked to “Always Day” once the time is changed to noon.
It used to not do that until this latest update. I used to be able to easily and quickly change the time of day with the “Time” button regardless of whether the daylight cycle was on or off.
I have a similar problem. I change the time to noon and it sets it to always day automatically. There's a temporary solution until Minecraft fixes this (if ever)