As the title implies, Riding merulina while under the effects of radiation (Through any means, such as friendly fire in the simulacrum, Death orb lasers or Radiation Hazard Sorties), casting and nearing Yarelis Riptide will cause the player to be stuck in place for a few seconds followed by the player falling through the map until they are teleported back up.  I discovered this glitch while playing through the (at the time of writing) daily sortie with my friends, which was a Radiation Hazard