I see two issues here involving the same problem of unnumbered print pages. First, about the TN on line 25. I'm not sure why there is a TN there in the first place. None is required in this situation. The TN required for interrupted text (covered in Section 3 (3.3.3) refers to the situation in which another type of text is interrupting the flow of ongoing text while print page numbering CONTINUES. That is not the case here and 1.10.6 which covered the absence of print pages does not mention or require TN. The absence of print page numbers and the text consisting only of picture captions conveys it all to the reader.
Basically, the concern is showing a page turn that occurs on line 25 of braille. When this happens with print page number, the next braille page will carry the next print page number and there is no problem. As you know, a page turn line is NEVER placed on line 25.
The same principle applies when there are no print numbers. The empty page turn line lets the reader know that a print page has been turned. In tracking the unnumbered print pages, the braille reader has the same information the print reader has--which is, not very much. The braille reader knows about the pictures and has no page number to refer to. Same situation for the print reader. In the case of braille, it doesn't matter whether the new print page happens to fall on a new braille page. There is no print page to refer to.
So here, do nothing. Insert page turns when you can. In this case, you can't. So don't. If you absolutely had to put a TN on line 25 for some other reason, follow the same logic. If there's no print page number anyway, it doesn't matter if the new unnumbered print page falls at the beginning of a new braille page. There is never a page turn indicator on line 25.