3406016 - After rejecting the flexible workflow, sales document is still in "In Approval" status

After rejecting the flexible workflow of a sales document, system doesn't change the status of the sales document from 'In Approval' to 'Rejected'.

There may be dump found as following at the same time:

Category               ABAP programming error
Runtime Errors         ASSERTION_FAILED
ABAP Program           CL_SD_SLS_COMP_APM============CP
Application Component  SD-SLS

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|Short Text                                                                                        |
|    The ASSERT condition was violated.                                                            |
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|What happened?                                                                                    |
|    The current application program has detected a situation with the                             |
|    ASSERT statement that should not occur.                                                       |
|    The reason for this runtime error was one of the following:                                   |
|    - For the checkpoint group specified with the ASSERT statement, the                           |
|    activation mode is "abort".                                                                   |
|    - A system variant has been used to set the activation mode to "abort"                        |
|    globally for all checkpoint groups in this system.                                            |
|    - The activation mode is set to "abort" at program level.                                     |
|    - The ASSERT statement is not assigned to any checkpoint groups.                              |
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• Sales and Distribution (SD) 
• SAP ERP 
• SAP ERP CentralComponent 
• SAP enhancementpackage for SAP ERP 
• SAP enhancement package for SAP ERP, version for SAP HANA 
• SAP S/4HANA 
• SAP S/4HANA Cloud Private Edition

SAP ERP Central Component all versions ; SAP ERP all versions ; SAP S/4HANA all versions ; SAP enhancement package for SAP ERP all versions ; SAP enhancement package for SAP ERP, version for SAP HANA all versions

ASSERTION_FAILED, dump, workflow, flexible workflow, CL_SD_SLS_COMP_APM============CP, CL_SD_SLS_COMP_APM, rejection, reason for rejection, BADI_SD_APM, IF_BADI_SD_APM~GET_SDOC_REJECTION_REASON, ASSERT lo_badi_sd_apm IS BOUND, CL_SD_SLS_COMP_APM, SD_SLS_DOC_SET_APPROVAL_ACTION , KBA , SD-SLS-WFL , Approval Workflows , Problem