We have to deal with a lot of phone footage nowadays, and the phones are prone to creating clips with variable frame rates, with some hit and miss results in post, particularly when using Premiere.
Have a look at this phone video clip specs:
If you are like me using BMD 3G Monitor with Desktop Video, with non legit frame rates in Premiere Source window, you get no output. Even though Premiere is content playing back the clip internally, no go with external monitoring.
Now if you create a legit frame rate Timeline and drop the variable FR clip into it, all is well because Premiere conforms the non-legit frame rate clip to the (legit) Timeline frame rate.
When bringing such variable FR clips into Premiere, the FR stamping gets somewhat fantastical. In this example I have 5 clips, all from the same phone. They are all recognized in the metadata as 29.98 fps:
Fro some reasons the first three clips playback just fine on the external monitor via Desktop Video/3G Monitor, the last two clips do not playback at all. Again, I'm talking about the Source window playback, not Timeline playback.

PP 25.5.0