IBR issue with PDFExportConverter/Optimization invocation

Ive setup an IBR instance with WCC 11.1.1.5 version to test out the PDF Optimization feature, using ootb PDFExportConverter,
and facing the following issue post checking in the content while actual transformation happens:

>refperformance/6 04.22 17:30:56.723 IdcServer-130 job progress for: 406 -- accepting job
>refperformance/6 04.22 17:30:56.738 IdcServer-130 job progress for: 406 -- putting in preconversion queue
>refperformance/6 04.22 17:30:59.660 Job_406_XXXXXXXVOTC3_4444 job progress for: 406 -- starting conversion
>refsteplogic/6 04.22 17:30:59.660 Job_406_XXXXXXXVOTC3_4444 Loading data for step: PDFExport
>refsteplogic/6 04.22 17:30:59.660 Job_406_XXXXXXXVOTC3_4444 Secondary Conversion step: PDFExport
>refinery/6 04.22 17:30:59.660 Job_406_XXXXXXXVOTC3_4444 starting conversion: PDF REFINEMENT; is subconversion: false
>refinery/6 04.22 17:30:59.660 Job_406_XXXXXXXVOTC3_4444 Script: TRUE
>refinery/6 04.22 17:30:59.660 Job_406_XXXXXXXVOTC3_4444 Evaluated to: TRUE
>refinery/6 04.22 17:30:59.660 Job_406_XXXXXXXVOTC3_4444 Script: CopyToWeb, PDFOptimization, ExecuteSubconversion<$subConversion='CreateThumbnail',supportsIX="true"$>