No point in messing with swappiness settings, trust me. You want to address the reason this happens in the first place, not disable to reduce swap.

I’ve had a nearly identical scenario at work. The reason? A data verification process that went through thousands of files to run their checksums and check integrity. This was working as intended, but the system alerts were firing because of that high buffer/cache utilization. So check which processes have highest IO and you might find the answer. Swap is just a side effect.