Welcome to the forum.
I am not sure why you are needing to compress the files from your Panasonic camera. What are the full file specs. from that camera, per your settings on the camera? I would think that they would Import directly, into a proper Project Preset for them.
Can you tell us what Project Preset you chose at New Project?
As you are experiencing a lockup, with Transitions, it would be good to know the full specs. of your computer.
This ARTICLE goes into more detail, on what info would be useful, and how to find some it.
According to this SITE, the camera shoots full AVCHD, but with several possible settings. Depending on those settings, the AVCHD files should Import perfectly into a full-AVCHD Project.
Good luck, and please let us know a bit more.