Wasn't one of the provisions that the buyer had to move the equipment with their own merchant fleet rather than US flagged ships? ...
I'd have to check. IIRC US flagged ships had some restrictions. It was not a serious obstacle since the US flagged cargo fleet was relatively small. Large US cargo ship owners preferred to flag the ships in low tax, low regulation nation's like Panama.
At the start the biggest obstacle was poor credit. Later in early 1940 as the Nav Cert system was stood up it became difficult for German purchasing agents to find ship owners willing to contract German purchased war material to nuetral ports. There were always smugglers, but as 1940 spun into 1941 those became increasingly rare & expensive. As the US became fully integrated with the Nav Certs system it became yet more expensive to falsely document and ship a war cargo to a German friendly nuetral.