After installing the "Knowledge Blocks" plugin the instance becomes unusableDescription<!-- div.margin { padding: 10px 40px 40px 30px; } table.tocTable { border: 1px solid; border-color: #e0e0e0; background-color: #fff; } .title { color: #d1232b; font-weight: normal; font-size: 28px; } h1 { color: #d1232b; font-weight: normal; font-size: 21px; margin-bottom: 5px; border-bottom-width: 2px; border-bottom-style: solid; border-bottom-color: #cccccc; } h2 { color: #646464; font-weight: bold; font-size: 18px; } h3 { color: #000000; font-weight: bold; font-size: 16px; } h4 { color: #666666; font-weight: bold; font-size: 15px; } h5 { color: #000000; font-weight: bold; font-size: 13px; } h6 { color: #000000; font-weight: bold; font-size:14px; } ul, ol { margin-left: 0; list-style-position: outside; } --> Symptoms After installing the "Knowledge Blocks" plugin the instance becomes unusable Release Seen in London, but issue could arise on other releases. Cause "Knowledge Blocks" plugin Resolution Clear instance cache, "cache.do"