I've work with python files idented with TAB
and I've noticed when I move ident back or forth with (command + [ ) or (command + ] ) it introduces spaces.
As it is difficult to differentiate in the code sometimes I use VSCode to change it back to tabs too.

other strange behavior is:
if there are 3 tabs, and my cursor is between the second and the third, if I use the shortcut to "select everything from the line start to the cursor" (command + shift + arrow left) it actually selects to the right.

Cheers!