Sorry for the issue. What is the exact file format & codec of the footage? Please create a new project & check if the issue persists.
What are the system specifications(RAM, OS, GPU model, GPU driver version)?
I have tried it with another project (with the same video clips).
Now I tried with older clips (that had no problems). They work. Only those newer clips don't. Weird.
Here are the details I was able to get (I marked which clip it is to the left-up corner):
PC specs are pretty new. (I built this myself 2 months ago)
Windows 10 Home 64-bit
Asus GTX 1070 TI
GPU driver: 391.35
Intel i7-8700 @ 3.7GHz
Asus ROG maximus x hero
Samsung 850 EVO
Corsair CMK16GX4M1A2400C16 Vengeance LPX 16GB (1x16GB) DDR4 2400MHz C16 XMP 2.0 High Performance Desktop Memory Kit - Black (name straight from Amazon)
I think PSU or fans don't matter.
Thanks for the detailed info. Please check if the files are getting imported as Audio only.
There is a known issue with the current version related to this.
If possible, share a screenshot of the Premiere Pro interface with us to understand better.