How can I determine if this frame rate issue is stemming from the clips I'm given or Premiere?

I'm working with a rather large corporation who is using proprietary software to restore footage from an archive. It gets restored at 59.94 frames per second, even though it was at one point shot on film or shot at 23.98 or shot in slo motion. This company will send me over 100+ clips in a day. And when I play the video in the source monitor, all of it looks great. but when I go to put it on a 23.98 timeline (yes i know its 59.94 footage), some of it looks great on the timeline, but some of it looks jittery/strobey. And there is one clip I ran into where a man was walking and the first few seconds of him walking looked strobey/jittery on the timeline but a few seconds later into his walk it was smooth again. It seems odd that a handful of these 59.94 clips look great on the timeline, but another handful of them look jittery/strobey on the timeline. Why those clips?  Again, if you match back to this clip in the source monitor theres no strobey/jittery issue. The issue is strictly on the 23.98 timeline. 

I know some work arounds to this issue but i'm trying to determine if the aforementioned information is an issue with the footage I'm being given or a Premiere issue. How can I determine that without posting the project file and clips publically?  (if you're interested in the 2 workarounds: the first is editing in 23.98, and then nesting the 23.98 sequence in a 59.94 sequence when I go to export, and stacking the problematic shots on v2 of the 59.94 sequence. The 2nd workaround is cut every sequence in 59.94 and apply posterize time to any shot that doesnt look 23.98).

UPDATE: I'm being told by an in-house employee: "I haven’t looked at the footage yet but I’m pretty sure I know the issue you’re having. It’s a known problem with restored footage. The way we have been fixing it is reencoding the footage with handbrake, media encoder doesn’t seem to work. Pretty sure there is some sort of meta data that Premiere interprets incorrectly. It’s a known issue they are working on. "