Hello. I have problem with fireflyes. Fireflyes show up only with Corona sun (with HDRI only - no fireflyes). Or, when I use Corona sun, but without bump on foliage.
https://drive.google.com/file/d/1Q7tEXmgNpEmq7NXwOzX80A32EMj0941Q/view?usp=sharing
This helpdesk article looks like it would cover this situation, see if the advice there helps - https://coronarenderer.freshdesk.com/support/solutions/articles/5000529356-i-can-see-bright-pixels-in-grass-