how did your enemies attack the party?
The only cases where I've seen something similiar so far is when the skills used a damage coding with special effects instead of the regular damage.
Please show us a screenshot of one of the skills the enemies use and that results in this.
It also could be that some of your plugins are not compatible with the game version - which version of the engine is that project based on?
Additionally, please give a screenshot of your plugin manager so that we can see if one of the plugins might interfere.