3540993 - "Article XXX XX is already included in other promotion(s) during sale period" - Message No. WU500 in BAPI_PROMO_CREATE

You are using retail promotions. When you create a promotion in T-code WAK1 and there is an other promotion already created during the same sales period for the same article, then system issues warning message WU500 "Article XXX XX is already included in other promotion(s)" during sale period. However, when you create the promotion via BAPI_PROMO_CREATE under the previously mentioned conditions, no warning message WU 500 will be raised. 

Article XXX XX is already included in other promotion(s) during sale period, BAPI_PROMO_CREATE, WAK1,  WU 500, Artikel XXX XX ist während des Verkaufszeitraums bereits in anderen Aktionen enthalten, Retail aktion erstellen, Retail Aktion hinlegen. , KBA , LO-RFM-MD-PR , Seasonal / Promotion Planning , IS-R-BD-PR , Seasonal / Promotion Planning , Problem