3790396 - Submission error when submitting DE_ECSL_DCL if report file generated as .txt

When attempting to submit the DE_ECSL_DCL report, the system shows the error: "The report run cannot be submitted. Check your entries."
The generated report file for a run is in TXT format and cannot be submitted.

A different run generates the file in XML format and can be submitted.
Observation during setup: SubmMode in customizing for DE_ECSL_DCL appears as "M" instead of "T" (not confirmed as the cause).

S4CORE 105
S4CORE 106
S4CORE 107
S4CORE 108
S4CORE 109

DE_ECSL_DCL, DRC, DRCc, ACR, Germany, EC Sales List, ECSL, ELSTER, ERiC, XML, TXT, submission error, the report run cannot be submitted, check your entries, report run , KBA , FI-LOC-VAT-DE , ACR Reports Germany , FI-LOC-ECS , EC Sales List , Problem