Missing EDI value after wm.b2b.edi:convertToString

Hi,
I got a question here that has been bothering me for the last few days.

I am trying to output an EDI 820 transaction by invoking wm.b2b.edi.convertToString, and the output T820T is legit. For example, in the attached picture file1, DTM Segment(Looped) is fully filled from DTM01 to DTM06. However, after the wm.b2b.edi.convertToString is called, the output EDI message is below, where a few elements are missing, particularly 01, 04 ,05. Same thing happened to those loop segments, where 01, 04, 05 are missing. What is odd is that unlooped segments like BPR work just fine.

So I have been testing and am not able to sort this out as to why EDI elements are missing while the T820T is complete.

ST820000000001
BPRD30000CFWT01121100782DA0544668008036976201322070381DA8003038539202004101
DTM**19940504
20200430*DTM06
SE
20
000000001

It would be highly appreciated if anyone can shed a light here.

Thanks.

file1.PNG