^{Update by Mega_Spud:}
Summary:
The subtitle command should appear if the command is executed whilst the title is still shown on screen. This setup allows a delay to be made between showing the title and the subtitle on screen, if the subtitle command is run after the title command using command blocks and repeaters, for example.

Steps to Reproduce:

1. Run the command /title @a title Title 123
2. Whilst the title is still shown, immediately run the command /title @a subtitle subtitle 456
3. Now repeat step 1 again

Observed Results:
The subtitle will not appear on screen after step 2, but only appears simultaneously with the title in step 3, and has no delay.

Expected Results:
If the subtitle command in run whilst a title is visible on screen, then it should show. This allows for a delay in the subtitle appearing on screen.

Screenshots/Videos attached: No

Notes:

Original Description:

I was using the /title and subtitle command, when I noticed that the title of the command block, was paried up with the subtitle command of another command block that wasn't connected to the pressure plate. The command blocks get mixed up with other command blocks, even though they aren't connected. Not only that, but when you try to use the title and subtitle command together, it will sometimes not show the subtitle, only the title, even though I set everything up corrcetly, but sometimes it takes two tries for both to work which is unfortunate. Please fix this, I really like the title command, but only when it works.