When attempting to update certain pages, they fail with "Paragraph delete operation failed" and the error [1] below is logged in the error.log. This error occurs on sites that are using Multi-Site Manager (MSM) where a Form component is on the page.
[1]
java.lang.NullPointerException: null at com.day.cq.wcm.msm.impl.postprocessing.GhostPostProcessor.process(GhostPostProcessor.java:86) at org.apache.sling.servlets.post.AbstractPostOperation.run(AbstractPostOperation.java:97) at org.apache.sling.servlets.post.impl.SlingPostServlet.doPost(SlingPostServlet.java:199)
Install the latest AEM 6.2 Cumulative Fix pack. The fix is included in the January 2018 fix pack CFP11.