RNIUSHCg== is actually easy to encounter.
If you don't know how you can encounter it, it has a 1/3 chance to appear after picking up a glitch fragment. If you don't encounter rush afterwards, then that means AR0xMBUSH or the SCJVEREECH swarm is coming. In order to get a glitch fragment, you need a natural (No admin panelling) Glitch spawn. The more glitch jumpscares, the higher the chance for a glitch fragment. 5 jumpscares, and glitch fragments spawning nearly guaranteed. (Unrelated note: Put together in the right order, the new letters of the glitch fragment entities, which are R0x, JVE, and NICg== spells R0XJVENICg==, which translates into 'glitch'. I wonder why.)