Ends voice immediately does not always work

Sometimes I have say a single note in a new voice. I need it just for a single spot. After that I get rests in that voice that won’t go away. When I attempt to select ‘Ends voice immediately’ Dorico wont let me, and just toggles the option off. What causes this? I come across it a lot. FWIW, I can set ‘Starts voice’ on the single note. Just sometimes the polyphony demands an extra note at certain points.

When this happens to me, I select the rest I want to delete and use the back arrow to find the note that precedes it. Then I can select the ‘end voice’ property and it sticks.

Same problem. I did not know that about back arrow - useful. But I go back a long way many pages before and the same problem occurs on that note.

I have encountered that when I mistakenly put a note or a few notes in the incorrect voice. If the pitch in the voice you visually associated with the following rests will not accept this toggle off, then it is in a different voice than the rests.

I have done this several times when I am composing. I rush to jot down a musical idea only to have it in the wrong voice…

Would it help you to identify which notes you have to give the ends voice attribute if you turn on voice colors?