Description

Users face issues when loading a Form (requester view). It's loading for a long time without success.
Here's a Blackbird (ctrl+F12) error recorded at that moment. + attached the same with details by each link.
Could you please clarify what it can mean?

debug:ru,en;q=0.9,en-US;q=0.8, Preferred: ru,en,en-US
debug:Unknown Translation key: textext
debug:renderCount==0, handled by jQuery onReady
error:ReferenceError: SVFormInternalOnFormPostRender is not defined
at HTMLDocument. (https://winshuttle.yourcompany.com/sites/WSUserGovernance/WinForms/_layouts/15/js/rt/view.js?build=11.20.01170.5093:127:13)
at fire (https://winshuttle.yourcompany.com/sites/WSUserGovernance/WinForms/_layouts/15/js/rt/require-jquery.js?build=11.20.01170.5093:4882:30)
at Object.fireWith [as resolveWith] (https://winshuttle.yourcompany.com/sites/WSUserGovernance/WinForms/_layouts/15/js/rt/require-jquery.js?build=11.20.01170.5093:4994:7)
at Function.ready (https://winshuttle.yourcompany/sites/WSUserGovernance/WinForms/_layouts/15/js/rt/require-jquery.js?build=11.20.01170.5093:2417:13)
at HTMLDocument.completed (https://winshuttle.yourcompany/sites/WSUserGovernance/WinForms/_layouts/15/js/rt/require-jquery.js?build=11.20.01170.5093:2112:10)

Here's also extract data from Console (F12):
VM277 sv.js:6916 [Deprecation] Synchronous XMLHttpRequest on the main thread is deprecated because of its detrimental effects to the end user's experience. For more help, check https://xhr.spec.whatwg.org/.
getLocalizedString @ VM277 sv.js:6916
(anonymous) @ VM277 sv.js:1

Applies To

Foundation 11.x and 12.x

Cause

Server run ouf of disk space.

Solution/Immediate Workaround

We could see that the storage for the site collection https://winshuttle.yourcompany/sites/WSUserGovernance which is located on the SharePoint Server was completely used while the issue was reported.
After we’ve emptied the recycle bin, the current storage used is 7500 MB out of total storage of 102400 MB.

If you do have performance issues  while loading a form make sure that you are checking 

Storage size on the SharePoint, Database Server, and all Winshuttle servers.

Additional Information