When maintaining a distance of roughly 15 blocks from an Osvermis, they will spam their attack sound/animation--without actually firing a projectile--as they slowly move toward the player.

Tested with Undead Rising as the only mod running.

To reproduce:

• Spawn an osvermis.
• Slowly move toward it, maintaining roughly 15 blocks of distance.
• Once it notices you and tries to attack, maintain distance by backing away slowly as it moves toward you, the spam will be obvious.

Fixed in the latest 1.2.4 version.

Download Link:
https://www.curseforge.com/minecraft/mc-mods/fishs-undead-rising/files/3282949