Model local thickening problem, UV-LCD anycubic photon mono 4k

Hi I have a problem with a printed model. UV-LCD printing, Anycubic Photon mono 4k. Also Anycubic resin, Basic. layer 0.015mm, time 1.5s, retract speed 2.5mm/s. A swelling/thickening appears when the two planes begin to converge. The model was hollowed and strengthened in Anycubic Photon Workshop v3.1. Does anyone KNOW how to solve this problem? I've also attached a picture (section3) to show what I mean. Thanks for help :*