Monero’s p2p layer is under attack for last few weeks. Someone is trying hard to jam the network.
There were/are multiple different attacks, summarized here:
https://sethsimmons.me/posts/moneros-ongoing-network-attack/
And here is video with Monero developer who implemented Dandelion++ discussing some of these attacks in more detail:
Becase these attacks are targeting p2p and Dandeion I tought it might be useful for Grin devs to check them out.