Corner Pin problem in Premiere Pro

Hey,
I have a problem with Premiere Pro showing lines-artifacts when using Corner Pin in a way that program
Task:

• General idea is to a add video to a mockup of smartphone.
• It requires cropping of a video which is recorded in 1920x1080;
• It requires placing cropped video on a mockup;

My way of dealing with it:

1. Adding cropping effect and cropping it + creating mask on opacity to round the corners.
   2. Using rotation, position and scale to roughly place video in the right spot.
2. Creating nest (*)
   3.  Adding corner pin effect and dragging points so it would fit the smartphone perfectly.
   (*) nest is applied to get corners of pin effect closer to the area that actually must be visible

Problem  - although it is the easiest way to to this it creates visual artifacts (lines) when perspective is pushed beyond what program thinks is acceptable, even though the perspective looks natural.
I had no such problems with other mockups (usually, artifacts appeared only when perspective was weird) but this one seems problematic for PP.

My solution (terrible one) - avoid corner pin and using Basic 3D & Transform. Way less accurate and way more time consuming.

I guess, I'm doing something wrong but it must be something obvious since I see no topics related to this issue.

I'm attaching video with visible artifacts + file of PP (with video clip and mockup) where one clip is created using corner pin and second one using transform and basic 3d.