Two of my biggest gripes

Sorry if this has been discussed before but I'd love if someone could help me understand if I've missed something.

When the teen gang were stuck in the upside down in season 4, they heard roars of what we assumed were gigantic monsters in the distance. Nancy also said Vecna showed her monsters invading Hawkins. Where tf were all these monsters in S5? Also what was causing the earthquakes in the UD? This was the only time earthquakes happened in the UD.

Then in S5 after Nancy shoots the exotic matter that caused the hole that sucked up Steve's car, surely that hole would've continued sucking everything up and destroying the UD? When they went back into the UD everything was stable again?

Such a disappointment all around, especially when in the documentary you see actors and writers asking valid questions and raising suggestions and just being ignored.