Timeline freeze when adding a video

Hi,

I already read some posts about the timeline freezing, but it's not the same problem that I have.
I have differents videos from the same source (old VHS that was numerised 20 years ago).
I can add some files from this video in Premiere Pro and it works fine.
But, as soon as I add some other files, the timeline not really freezes, I can still use it, but I can't see what I am doing (like reducing the lengh of a video or moving the cursor).
I use the 15.0.0.0 version of Premiere Pro on a Dell G5 (march 2020) and Win10.
All the files I use are from the same source (a 55 min long mpeg file I cut in smaller files).

Any ideas?