All in Premiere Pro 2018: From the top,
I began by having exported videos in H.264 format export without XMP metadata, rendering them unplayable in the default Windows 10 desktop video player (Movies & TV I think its called). It didn't give me any sort of error message the first time I attempted to export it, so it was a surprise to be hit with the windows error message for an unplayable file type. On the second attempt prior to exporting, a popup came up saying that it would export with incomplete XMP metadata, so I stopped and searched for any forum posts to try to fix my problem (the only ones I found were wholly unhelpful and from 6 years ago now so needless to say I was on my own). I then proceeded to clear disk space and insure it was exporting to the right location, which helped nothing. The issue was finally remedied by switching the preset export from Match Source- High Bitrate to Custom with the same settings as the Source had. Your guess is as good as mine as to why it worked (and before anyone says it, I did check to see whether "Export without XMP" was checked in my preferences).
Other than the export issues, I have had the Program window totally whitescreen until I either ran the circuit of all the preset workspaces, or saved and restarted the project. Occasionally it would also become a hodgepodge of the neighboring panels, duplicated one on top of the other inside of it.
I have had the program stop responding multiple times now just from attempting to save as, both when attempting to rename the file before beginning exporting.
Last and worst of all, I have had two different files inexplicably lose the whole, completed video in the timeline. I discovered this when I was attempting to use the same color grading that I had in a previous video, so I opened said file in the project I was working in. Rather than adding a second source to click, it just opened the project files in the Project Panel. Puzzled, I closed what I was working on and went back to the project I was attempting to draw reference from. I came to find that the timeline was totally empty. I didn't save after deleting it and I most definitely don't recall doing anything that would warrant the erasure.
I use a 2017 Lenovo Legion Y520 Laptop with 16GB RAM and an Intel core i7- 7th gen processor