It is hard to say what might be the reason without knowing your scene and settings, but the issue looks like a combination of too strong denoising and bad Cosmos browser materials.
Some Cosmos browser models come with, let's say questionalbe material settings that may stem from an automatic conversion of the materials from Vray to Corona. Often you will find an IOR of 1 and a glossiness of 100. So, checking if a material makes sense is helpful.
What denoising settings are you using, btw?
Michael