Hi Rohan,
Please check the below note very close to your issue and see if it helps.
1516778 - An internal error occured while calling 'answerPrompts' API. (Error: ERR_WIS_30270) in WebI report
Also, please provide more details such as environment BO/BW versions and check and give details as to which type of Bex variables(single value/multiple single/selection option/interval)/prompts(optiona/mandatory) is this issue specific to?
Thanks
Mallik