I found, this is an issue with multiple forms, with same fieldnames, but different mediasources for the same fieldname.
can you try to use different fieldnames for the url, for example something like that:
[
{"formname":"PDF", "formtabs":
[{"caption":"Lgg till", "fields":[
{"field":"pdfurl","caption":"Fil","inputTV":"fileTV"},
{"field":"title","caption":"Titel"}
]}]
},
{"formname":"URL", "formtabs":
[{"caption":"Lgg till", "fields":[
{"field":"url","caption":"URL","inputTV":"urlTV"},
{"field":"title","caption":"Titel"}
]}]
},
{"formname":"Seminarium", "formtabs":
[{"caption":"Lgg till", "fields":[
{"field":"seminarurl","caption":"Seminarium","inputTV":"seminarTV"}
]}]
}
]