I'm using Kdenlive 17.12.1 (version not available in bugzilla at the time of reporting). All my clips are 1080p 60fps. The default profile is 1080p 25fps. The setting to ask to change the project profile to match the clip was disabled after install. I didn't notice it until now. Changing the project profile after editing to match the clips reduces the time for each clip, and some clips are cut or missing. If the clips already match the new profile, IMO this should not happen, or the user should be asked if he wants to alter the timeline clips to match the new profile, or be smart enough to notice that the clips profile matches the newly set profile.
This could be a duplicate of Bug 350948, but that bug's comments state that it's been fixed, I'm guessing in git master, but I still see the bug 2 years later in a released version. I'm not marking it as a duplicate yet. I'd like some feedback before that.
I had the same problem in 18.08.1. Opened a project in default setting 1080 25fps, started editing (clip was 720x480 30fps), then decided to make the project profile also 720x480 30fps, continued editing, and then noticed at the end that the editing I did before the profile change was messed up (all cuts were off by say a few seconds).
The relevant bug for this, that has already been filed, seems to be 368962 (https://bugs.kde.org/show_bug.cgi?id=368962) to me?
I confirm, this is the same issue as bug 368962. *** This bug has been marked as a duplicate of bug 368962 ***