Weird light on plane intersections

[buncha]

https://imgur.com/a/bcYiM

i really don't know what could be. there are no 2 planes, it is only one, model is from Archi CAd

[romullus]

This looks like too low  UHD cache settings. Could you look to render setup>performance>uhd cache and tell what value is precision set to.

[buncha]

I'm sorry i got settings from client but obviously they weren't good. I just put back everything to default. now the image looks really clear but i still have some weir gradient on walls. i am using a texture in diffuse which i was given by the client. what that gradient could be? i have only 1 corona light directly over the apartment
https://imgur.com/a/CB6ts

[romullus]

It's hard to say without having scene itself. Could be some invisible light, or low quality texture of the wall.

[maru]

I am not sure, but it looks like there is heavy denoising used in this render. This could cause such artifacts, so the solution would be to render for a bit longer, and then apply lower denoising.