Free Libre 2 EU calibration and value issues

Hi - great app - sadly ,the data displayed from an Abbot Free Libre 2 EU version is very wrong - I tried calibrating it via a custom offset - but it seams to not just be a systematic error - since the error is not linear and the calibration does not fix the issue.
Libre Link shows some quite different values. 

Any idea why - and how to fix this?