I continue to hit this problem but have developed a workaround that has worked so far.
During Project A I inserted Video B at 1:32-1:42 and Video C at 1:53-2:01. Upon Exporting, there was freeze from 1:43 until 1:53 (the frame AFTER Video B finished was frozen lasting until Video C started). I replace Video B with Video D for the exact same amount of time in the same spot and got the same freeze.
Workaround -
I cut Video B/D out of the Sequence (but left them in the Project) and exported with only Video C (which worked fine the whole time).
I then renamed my project to "Project A Final" and saved it as a new project.
I added a new Sequence and brought in the video of "Project A" and placed it into Sequence 2. I then put Video B back on Sequence 2 where I wanted it on Project A Final, Exported Sequence 2, and <drum roll> it worked! No more freezes!!
Now here's the part that bothers me the most Videos A, B, C, D were either shot with the same camera at the same rates and exposure OR were a screen capture of a PowerPoint Presentation using NCH's Debut software. In other words, I kept thinking the root of the problem had to be because I was mixing and matching from other sources but my sources are all the same. I was convinced it was something about mp4 vs. avi or incompatible frame rates or something. But none of those things seem true now. Messing with frame rates, output type, encoder values, etc. never got me where I wanted to go and quite frankly, got pretty old!
To me, here's the BIG QUESTION: Why would Video C work no matter what I did but Vidoes B and D did not work no matter how much I tinkered with the settings? It makes no sense to me and obviously is going to be very tough to debug. To be clear...ALL Video A is an output of Debut with some "live shots" from Video B and C now cut into it. However, C is cut into the original and B is cut into the output of the original project as a new Sequence/Project.
Developers: I know you want to get your hands on my videos to see if you can replicate this. Unfortunately, these are not videos that I can share. However, now that I know what I'm looking for, I think I can recreate the same circumstances in a less than 3 minute video and put the project/video files in a Dropbox for you. However, it might be a week or more before my schedule will allow me to do that (business travel, etc.) If I can get to sooner than that I will. I know I've been hard on you in earlier posts but I have a lot more sympathy now that I see how odd and illogical the problem is. After 30 years in the IT industry, I can bet this is going to turn out to be some minor change that that no one ever considered possibly impacting ANYTHING.
What smells really fishy to me is that several of us started complaining MONTHS after v5.01 was released. Which makes me think that whatever has triggered this came to us later in the form of Microsoft update or something like that.
(Oh BTW - The computer I'm using to do the work is a Dual Core i7, 16GB memory, Geoforce GTX, <insert male grunting noise here> etc. So it's not the hardware slowing anything down or fighting for some system resource - All work (project files and Exported files) is done on an external drive with all caching on the C: drive - That's not to say this isn't hardware related - can't eliminate it yet, I'm just saying, there's not an obvious answer there either).