Why do tabs close in Sublime text 3?

Question

Sublime Text

If necessary, you have to work in a window divided into 6 code areas. Each of which has 3-4 tabs open. I open the necessary file through ctrl + p + its name.
However, at a certain moment. in another area, one of the tabs closes. It looks like an open limit. But I have not been able to find out by experience.
I would be grateful for any hint or idea.

Answer 1

Plugin may be installed: Zen Tabs . In its settings, the limit of open tabs is set.

{
    "open_tab_limit":  10
}