Error when calling long text processing

What causes this issue?

Before the system can call the long text editor, it needs to read the
text from the database, create a temporary copy, and so on. This is
especially true when you work with a change number.
An error occurred during one of these steps.

System Response

The system terminated long text processing. The data remains unchanged.

How to fix this error?

Call some other entries to check whether you have a general problem in
long text processing. If this is the case, you probably have a problem
in SAPscript. Exit the screen by choosing <LS>Cancel</> to prevent
further damage to data in the database.
If you are using a change number, repeat all steps that led up to the
error without using a change number. If the error still occurs, you
probably have an problem in SAPscript. However, if the long-text editor
is working perfectly, the problem may lie within Product Safety and
Stewardship.
Contact your system administrator to correct the error.

Error message extract from SAP system. Copyright SAP SE.