Error while editing adaptive form "org.apache.sling.api.SlingException: Cannot get DefaultSlingScript: org.apache.sling.api.SlingException: Cannot get DefaultSlingScript: org.apache.sling.api.scripting.ScriptEvaluationException: "

Seen this issue with multiple times and the cause for the issue is not clear:

1)- The issue is not AEM Forms version or service pack specific as it was seen with other versions of 6.5.

2)- When we try to preview the form it shows below error page

3)- When this error comes forms doesn't load in authoring mode too and shows only template level items like header or footer.

4)- Below is the complete error trace:

org.apache.sling.engine.impl.SlingRequestProcessorImpl service: Uncaught SlingException
org.apache.sling.scripting.sightly.SightlyException: org.apache.sling.api.SlingException: Cannot get DefaultSlingScript: org.apache.sling.api.scripting.ScriptEvaluationException: 
	at com.adobe.cq.sightly.WCMScriptHelper.includeScript(WCMScriptHelper.java:227) [com.adobe.cq.sightly.cq-wcm-sightly-extension:1.6.0]
	at com.adobe.cq.sightly.internal.extensions.IncludeExtension.call(IncludeExtension.java:72) [com.adobe.cq.sightly.cq-wcm-sightly-extension:1.6.0]
	at org.apache.sling.scripting.sightly.impl.engine.runtime.RenderContextImpl.call(RenderContextImpl.java:77) [org.apache.sling.scripting.sightly:1.1.2.1_4_0]
	at org.apache.sling.scripting.sightly.libs.fd.af.components.page2.aftemplatedpage.afpagecontent_html.render(afpagecontent_html.java:113)
	at org.apache.sling.scripting.sightly.render.RenderUnit.render(RenderUnit.java:50) [org.apache.sling.scripting.sightly.runtime:1.1.0.1_4_0]
	at org.apache.sling.scripting.sightly.impl.engine.SightlyCompiledScript.eval(SightlyCompiledScript.java:60) [org.apache.sling.scripting.sightly:1.1.2.1_4_0]
	at org.apache.sling.scripting.core.impl.DefaultSlingScript.call(DefaultSlingScript.java:386) [org.apache.sling.scripting.core:2.3.2]
	at org.apache.sling.scripting.core.impl.DefaultSlingScript.eval(DefaultSlingScript.java:184) [org.apache.sling.scripting.core:2.3.2]
	at org.apache.sling.scripting.core.impl.DefaultSlingScript.service(DefaultSlingScript.java:491) [org.apache.sling.scripting.core:2.3.2]
	at com.day.cq.wcm.tags.IncludeTag.includeScript(IncludeTag.java:178) [com.day.cq.wcm.cq-wcm-taglib:5.13.8]
	at com.day.cq.wcm.tags.IncludeTag.doEndTag(IncludeTag.java:95) [com.day.cq.wcm.cq-wcm-taglib:5.13.8]
	at org.apache.jsp.libs.fd.af.components.page2.aftemplatedpage.aftemplatedpage_jsp._jspx_meth_cq_005finclude_005f2(aftemplatedpage_jsp.java:512)
	at org.apache.jsp.libs.fd.af.components.page2.aftemplatedpage.aftemplatedpage_jsp._jspService(aftemplatedpage_jsp.java:408)
	at org.apache.sling.scripting.jsp.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70) [org.apache.sling.scripting.jsp:2.3.6]
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:764) [org.apache.felix.http.servlet-api:1.2.0]
	at org.apache.sling.scripting.jsp.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:502) [org.apache.sling.scripting.jsp:2.3.6]
	at org.apache.sling.scripting.jsp.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:449) [org.apache.sling.scripting.jsp:2.3.6]
	at org.apache.sling.scripting.jsp.JspScriptEngineFactory.callJsp(JspScriptEngineFactory.java:339) [org.apache.sling.scripting.jsp:2.3.6]
	

5)- One option to recover from this scenario is to replace the form with another copy from other environment.