'Please correct the errors highlighted below and try again.' error since last

I have updated my Metabox plugin as per the new update and since then I am getting this error: Please correct the errors highlighted below and try again.
whenever I am trying to modify my old posts with any new information.

This is weird. I checked very carefully but there is no empty fields which are mandatory. In fact I tried a few other posts and simply clicked 'Update' still I am getting this error.

This means it has something to do with new updates.

Please look into this.