Dobson double image issue

Hello, I have a problem with my dobson telescope. When I try to focuse on star or a planet I get double image. Like when I try to gradualy focus on a star first what I see is the image of the secondary mirror but when I continue focusing instead of a single star I get two images of the same star getting closer to each other but never merging after they ''pass'' each other the image goes back to being unfocused.

On a planet it looks like this:


Could it be that there is some thin film left on the mirror after cleaning or something else?