I had problems with PowerDVD awhile back playing newer BD discs and went to Total Media Theatre 3 which I've had for some time. Oddly enough, this older software had an update still available which corrected the problems, similar to yours, I was having.
Newer BD discs can be problematic possibly because of problems with DRM. Try an older BD disc and see if it plays fine. Then see if Cyberlink has any updates for the PowerDVD version you have; that may correct the problems. You may also need to check if there are any firmware updates available for your external BD drive. To check this, open Device Manager as Administrator, and I expect you'll find the external drive under Portable Devices, double click your BD drive, go to the details tab, then under the Property drop-down menu select "hardware lds". There should be an alpha/numeric number on the far right and this is your firmware version. Check the manufacturer site for any updates and how to proceed installing it.
You might try a different player as well, perhaps WinDVD.
Hope something above helps.