Issues and artifacts with Corona 15

Hello. I have a batch rendering process where we render 200.000 images a month for 360 renders. I use a corona shadow catcher in it composoting mode to get shadows with the transparent background. but after the update I got a weird little shadow artifact in the back of the chadow catcher. seen here. and the model and scene and lighting is not changed. not at all. but it appeared after the update. so I guess my question is. can it be the update that introduced this?
Understand if you need to see the scene futher to check it. and if so I can upload.

Latest windows, 3dsmax 2024

here is the shadow catcher. I have put it in a layered material with a slot of a invisible material to control the shadow strenght. and I use a shadow catcher Light as well that is only effecting the shadow catcher plane.

It looks like the edge of the shadowcatcher with something casting shadow on it. Please contact us about this here and attach your scene - ideally, please attach the original scene saved with Corona 14 or older where the problem did not occur - https://support.chaos.com/hc/en-us/requests/new