Cut problems - selection jumps

Hi everyone,

I have an annoying problem during the cutting process. When I select my clip for the second cut, from time to time, the selection jumps.

So my normal process is:

first cut (Ctrl+K), second cut (Ctrl+K), and delete (Shift + Delete).

But from time to time, the selection jumps to another section, and I end up deleting the wrong area. You can see it in my attached GIFs (In both clips, you can see the problem occurring at the last cut).

By the way, as you can see in the second clip with three tracks, is there an easier way to select (all) tracks for the second cut, or is 'A' (Track Select) and mouse selection the fastest way?