White Triangles in Upper Corners disappeared and Sequence Close Cap not working

[alfrexr78659032]

As you can see in the video the white triangles disappeared and when I dragged something it's overlapping/overwriting my clips.

Any idea how can I fix it?

https://youtu.be/E02riTZu_ro

[Ann Bens]

Turn on Snap(S).

EDITED.

[alfrexr78659032]

I pressed the S while selecting the timeline and didn't work

[Ann Bens]

Snap (Magnet) is a setting which is either on or off.

The white triangles indicate the first or last frame of an untrimmed clip.

As soon as the clip is trimmed, or you overwrite a clip in the timeline the white triangle disappears as it no longer showing the first or last frame.

[alfrexr78659032]

Yeah, I checked other threads but what should I do?