Request campaign API call - why does a overridden text token not work in a 'Change Data Value' flow step?

Hi there,

We are overriding a text token in a smart campaign via web service API. e.g. text token {{my.variable}}

In the flow step, we use 'Change Data Value' to set a custom Marketo Field to the overridden token, so we can use that token in a velocity script in the email we send.

It works about half of the time, and does not work the other half. We cannot figure out why.

Have attempted wait steps before data value change, after data value change, spaced out all flow steps a minute or two, etc. It continues to work some of the time, and not work other times.

Lead activity shows that the data field change is not made for leads where it does not work.

Any insight appreciated.