try rendering with displacement unchecked, i had this along seams of a garment when i used irregular displacement maps

 

if its that then you can change the displacment to mid grey around the seams on both areas where they join,

 

ill try and find the thread i started when I had issues,

Tools:- Win10, Dell XPS8900, ZBrush, Marvelous Designer 11, Hex 2, PSP8. PSP 2019 Ultimate, DAZ Studio, Affinity Photo, Affinity Designer, Filterforge 11, flowscape,  Classic UVMapper, and several headache tablets.