Hi there @wardy_mk,
Thank you for your reply.
Could you please let us know what lights you're using for your scene project?
Additionally, could you please try rendering a test image setting the "GI/AA balance" (which is located in the Corona Render Settings->Performance Settings) value to 8, and then please do another test with a value of 24?
One last thing: could you please try using the Intel denoiser instead? (don't forget to use the "Tent" Image filter along with the Intel denoiser. (you can change the Image filter at the Corona Render Settings->Frame Buffer Settings->Image filter)
Please let us know the outcome.
Kind regards.