Hot or hot?

I would guess that they are getting strong and have a few more bees than before so can afford a defense team.
Pinging off the veil and/or buzzing near the veil is part of how they defend themselves.
Ever notice how drones will ping too?
Just because they are threatening you when you "attack" their hive doesn't mean they are hot. It means the bees are healthy.
Stay calm while they ping and they will stop.
They are testing you.

Use smoke wisely, keep them from winding eachother up, this is all part of growing colonies.

very normal

Ditto

Thanks for the info. I had more advice from a local beekeeper, and he suggested it was because there isn't much of a flow right now and they're defending what they have from potential robbers and hornets.

Bees are so interesting and multi-faceted.