PdfViewer/Form/Fullscreen issue (F11)

Hi!
I have a form (not maximized) with pdfviewer that loads from stream, no problem.
But if I maximize the form (from control box title form) and then press F11 (enter browser fullscreen) throws a wisej modal error, see attached image.
Tested only in Firefox 54.0.1, 55.0.2 and InternetExplorer 11.1480.14393
I’m using (personal) stable wisej version 1.3.75
Thanks in advance.