^^^ I originally thought the issue could be disk related. I went and bought another episode of Star Wars 7 some months later after watching the episode repeatedly on blu-ray and then going back to the 4K only to be disappointed. The new disk hung up in the same spots intermittently as the first did. I assumed having waited several months to make the purchase the new disk was from a different batch run. So that technically eliminates "bad disk" as a probable cause. Glad you are having success with your unit. I would not wish this on anyone. It is embarrassing and frustrating when watching a movie with guests over and the unit locks up. Currently all testing using the Panasonic UB420 unit have proven the disks that failed to run consistently without issue in ANY of the 3 Sony units I owned, to run flawlessly as designed with ZERO issues. This is with identical connectivity as used with the Sony units. The only thing I am considering is upgrading to the UB 820 as it has an improved processor that is being raved about. Sorry to burst any devoted Sony brand bubbles, but Panasonic seems to have a better handle on either processing or handling of the disk in the carriage assembly one way or the other. I can find no other explanation.
Having worked directly for and with over seas manufacturers (across the Pacific as well as across the Atlantic) at a technical support level, I know first hand the arrogance that can play into situations such as this. I call it the "Big Pond" dodge. It's like trying to get technical support or a sales quote locally in NA via email request verses a physical phone call request. The first they can blow off, the second they are stuck dealing with directly. Distance makes it more difficult to get OEM's to admit they have an issue.......unless they have a large NA presence. It is only when these OEM's start seeing a larger scale issue (usually on their home fronts) that the issues begin getting attention, and then they will often give excuses, attempt coverups through unannouced tech pub updates and/or firmware upgrades, and take credit for finding the issue and resolving it themselves. The US suffered from this in the 70's massively in the automobile industry. It took decades to catch up. But that is another story.
Thanks for your input. I do appreciate it.