An error occurred during the update

What causes this issue?

During activity price calculation posting, a serious system error
occurred. The calculation, however, has already been partially posted.

System Response

Processing is terminated.

How to fix this error?

For more information on the error, see the error description in the
processing error log.
No inconsistent data was created during the posting. You should
nevertheless restart activity price calculation after correcting the
error in order to make a complete posting.

Error message extract from SAP system. Copyright SAP SE.