Seems like I'm not lucky with testing those scripts and I've already spent an insane amount of time trying to reproduce this.
Using "Traxsource Release Search by Artist - title" with "Doug Gomez Puro" gives no results and using "Traxsource Track search by artist-title" with "Doug Gomez Puro" gives a valid result including title and cover art.
Please just share what you are using to produce the error.
I've checked this further and I had a one-off error in validating the function parameters in web sources scripts, so that those would never be checked.
With the latest additions I needed to extend the maximum number of parameters per function from 3 to 5, so that the 3rd parameter was now checked too. We also had this before in our conversation via PM where the superfluous parameter for debug suddenly caused problems.
To make life easier for all of us, I've now extended validation and also added reporting of syntax errors via an error message with Mp3tag v3.21c.