Try...
<autoadd thing="wpBEAxeTh"</autoadd>
I will tell you, that once you get it working, you may not like it. The granted items currently cannot be discarded.
EDIT: Missed the bit where you said the problem was when it was added as an advance... More testing here.
This worked fine as an advancement edge:
<thing id="edgTSTgonz" name="Gonzo With the Gear" compset="Edge">
<tag group="EdgeType" tag="Background"/>
<tag group="MinRank" tag="0"/>
<autoadd thing="wpColtDrag"></autoadd>
</thing>
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