Inkonsistency of storing payload

[Pymann]

Jenkins and plugins versions report

plugin version 2.4.1

I have two jobs and store root of payload into variable with "$" as jsonpath, variable-name is GWT_PAYLOAD

and in another job I do same but additionally save some headers (only difference, that I have noticed)
for any reason GWT_PAYLOAD look different for both jobs, in first case ise {"payload": [<real-payload-string]} and in second case it is:

[tomasbjerre]

It is empty? Is that in the job that also has headers?