Thank you for your post.
Since this happens occasionally, please post the script steps being used so I can try to replicate it here.
What is the predominant browser and version being used that encounters this issue? I'll try each browser, but if it occurs more often with one, I can repeat the steps multiple times using that browser.
The link above does display "Hello World". On a separate issue, there is no option to close the file.
The test file (Hello World) posted is there to illustrate that the issue exists with even the simplest of databases, it is not meant to be a functional database. The file used can be downloaded from here for your own testing.
I just refreshed the browser (pick one, they all do it) on the test file and it is stuck on a blank form with the status bar displayed. Clicking anywhere in the browser brings you to the opening layout as defined in the startup script. It cannot be the desired functionality to have the file hang randomly.
This is a huge issue for my client, and I am at a full stop with this project. Deadline looming nearer, need a resolution or will have to abandon FileMaker for this (and future projects). Shame of it is, WebDirect works great for the kinds of projects I typically have minus this quirk.
I downloaded the file and have it hosted on a Windows Server 2008 R2 and Mac OS X 10.9.5, both running FileMaker Server 13.0v4. I am still unable to replicate the issue with Chrome (Windows) and Safari (Mac).
What is the operating system of the n38.fmphost.com server?
Looking at your script, could it be a refresh issue? Try clearing the cache, or add a "Refresh Window" script step to the end. Does this help?