The issue seems to appear only on specific parts where LOD 0 transition to LOD 1 happens. I’m going to zoom in on these two spots:
http://uupload.ir/files/mrd4_1.jpg
Red spot from close up looks fine:
http://uupload.ir/files/ojjf_2.jpg
Blue spot from close up looks uneven:
http://uupload.ir/files/xnob_3.jpg
In 4.18 and before, blue spot starts to look just like red spot when approached.
In 4.19 this uneven-ness (new word?) in triangle size makes some tris become way denser than others when tessellation is enabled.