The following screenshots show a Pipe - 45 Degree at 10x scale with rotation (121, 0, -90) and the material Stone - Basic applied. The scene uses Sky Core default with the Sun Light rotated at (0, -90, 0).
Part of the interior of the pipe at this scale renders with shadow artifacts when viewed up close. The artifacts appear at any object scale above 3x, and at any rotation that creates a shadow inside the pipe.
DFL not disabled, artifacts appear up close:
DFL disabled, no artifacts at same viewing distance:
DFL not disabled, minimum distance at which artifacts disappear:
DFL disabled, at minimum artifact-free distance of course shadows aren't rendered well: