Ok I'm back in v6.
I've loaded 39 clips that total 22 minutes of iphone 1080 60fps .mov files. It can't seem to handle it. I'm trying to export the whole thing to mp4 and then will try to work with that. Updates coming...
Update #1 Exporting the original clips to single 3.3GB 60fps 1080p MP4 file took 73 minutes.
Update #2 the newly loaded file is half way green-cached. I split the clip 8 seconds in and now anything after that split is stuck "building preview, please wait." However the time is still advancing along with the audio. I will try again if and when it completely caches.
I would have lost this bet... I really thought a single 22 minute already converted to mp4 file would have worked.
Update #3 Fully cached, computer CPU not working on it anymore. Still stuck in building preview after first and only edit, that first split.
Update #4 Tried hardware accelerated video effects unchecked and restarted program. No Joy. Cached, but stuck on "building preview please wait" along with sound and time progressing.
Update #5 Lowered the preview res to 512x288 and 25 fps. Even before caching it immediately works as expected. Is it viable option for me? No, because < 12 fps in slow is too low to view at this res (accidentally put missed buckets in the highlights). But hopefully this is helpful to target core issue. I can also add that issues seem to be unrelated to computer resources which were never near max. Limitations in higher preview mode seems to be related to videopad.