New Post: CPU 100% w3wp after C1 run for a while, what's rootcause?

@mawtex,
I can see the following log repeated in App_data/Composite/20160401:
20160401 06:56:08.9547 2 48 Warning /Renderers/Page.aspx  Failed to format output xhtml. Url: /help/souhupai
20160401 06:56:10.2047 2  6 Warning /Renderers/Page.aspx  Failed to format output xhtml. Url: /help/souhupai
20160401 06:56:12.0329 2 47 Warning /Renderers/Page.aspx  Failed to format output xhtml. Url: /help/souhupai
20160401 06:56:13.2517 2 19 Warning /Renderers/Page.aspx  Failed to format output xhtml. Url: /help/souhupai
20160401 06:56:15.5798 2 47 Warning /Renderers/Page.aspx  Failed to format output xhtml. Url: /help/souhupai
20160401 06:56:17.9862 2 50 Warning /Renderers/Page.aspx  Failed to format output xhtml. Url: /help/souhupai
20160401 06:56:18.0799 2  7 Warning /Renderers/Page.aspx  Failed to format output xhtml. Url: /help/souhupai
20160401 06:56:20.4706 2 54 Warning /Renderers/Page.aspx  Failed to format output xhtml. Url: /help/souhupai
20160401 06:56:22.2675 2 19 Warning /Renderers/Page.aspx  Failed to format output xhtml. Url: /help/souhupai
20160401 06:56:24.7520 2 36 Warning /Renderers/Page.aspx  Failed to format output xhtml. Url: /help/souhupai
20160401 06:56:28.0333 2 19 Warning /Renderers/Page.aspx  Failed to format output xhtml. Url: /help/souhupai
20160401 06:56:28.2833 2 54 Warning /Renderers/Page.aspx  Failed to format output xhtml. Url: /help/souhupai
.....

can you find something?