Cannot delete empty standard fieldset

[floseries]

easyform 4.0.0 in Plone 5.2.8 py 2.7

Having several fieldsets filled with fields, I want to delete the empty Standard fieldset.

Standard fieldset does not appear in the XML fieldmodel.

Trying to change second fieldset name to "standard" and saving is not working. The URL including the XML description exceeds the capacity limit of the server.

Regards
Fritz Loseries