RHI flush resources costly

I am optimizing a scene in my game, and I’m currently getting stuck on my rendering thread. I am seeing large costs appearing in the FRDGBuilder, specifically EndFlushResourcesRHI, which sometimes spikes up to 11-14ms for a few frames.

What would be the reason for such a high amount of resources flushing? Is there a way to profile further? or is there an overarching reason for this?