Cannot assign variable inside "foreach"

Summary:

Cannot assign variable inside "foreach"

Content (please ensure you mask any confidential information):

upon trying to assign value of a node from node-set which has a specific field's value inside a foreach loop,

I am able to complete the assignment on the first iteration, but the next iterations fails.
getting: "The result of from-spec is null."

Version (include the version you are using, if applicable):

Code Snippet (add any code snippets that support your topic, if applicable):