If you have finished all 10, I don’t know what this last ‘strip’ is you refer to, but there are only 10 films and you say you finished printing all 10. ?

black pictures are a shutter problem, no light is getting in and how can it put the image on the film if it doesn’t open, or barely opens. Never shake the picture, it will splatter the chemicals around unevenly and cause defective developing. NEVER OPEN the film door unless it is showing a 0 that means it is out of film, or you will be the exposing the film by letting light onto the film and you will get all white pictures, since you are not supposed to be the shutter. It will also reset the camera pics left to 10, so once you shut that door, leave it shut. If you have some in there that you already opened on, It could be that only the next film will be ruined and some after that will work, so don’t just throw it all out. Flow chart: Camera needs film->open camera, insert film, now it says “s” - think of the s as meaning ‘shade’, telling you the shade is still over the film. Depending on the camera, some will automatically release the shade when you power on, if not, then the first time you go to take the...