Kdenlive will freeze and the saved file will become unusable if any of the compiz features are turned on, such has the wobbly windows, for example. There needs to be a warning message saying compiz isn't compatible with all software or better still take compiz off the default install in the next Kubuntu release in October 2016.
When the software does go up the creek the average user will not know it is because of Compiz. I had to look into this deeply and think about the last action I did to cause the bug. It was a bit frustrating considering I spent a very long time putting my video together.
The second bug, and I do class this as a bug but others will not... When you remove Kdenlive (or any software) from your system either by the termininal or using the package manager the software just becomes hidden it doesn't actually uninstall completely. I did follow the sudo remove command with the purge command however, when I went to re-install Kdenlive it wasn't a fresh install, it installed with all the faults in tacked forcing me to completly re-install Kubuntu.
Thank you for taking the time to report this bug and helping to make Kubuntu better. We are sorry that we do not always have the capacity to look at all reported bugs in a timely manner. There have been many changes in Kubuntu since that time you reported the bug and your problem may have been fixed with some of the updates. It would help us a lot if you could test it on a currently supported Kubuntu version. If you test it and it is still an issue, kindly upload the updated logs by running only once:
apport-collect 1578646
and any other logs that are relevant for this particular issue.