I tried to import a slow mo clip from my phone, its 257 fps…the program crashed…tried two times…same thing happened. Its from a samsung s9
Did you open your Film in VLC and looked for the metadata? What does it say?
I have a 240 fps GoPro clip that works fine for me. Keep this in mind: if you are using Settings > Video Mode = Automatic, then change it to something desirable and then try to bring that clip in. Otherwise, if this is the first clip you are opening, then the project will be set for the 257 fps. In order to take get advantage of a high frame rate clip for slow motion, the project needs to be at a lower frame rate. Then, when you use speed to slow it down, it takes advantage of the additional frames to make it smooth looking. I hope that helps.
If you want to donate that clip to me to try to debug the crash, please upload it somewhere and provide a link. I can also private message you a link to where you can upload.