Hi. I describe a rare bug seen in today's org-mode (8.3.6) running in emacs 26.0.50.1.
1. emacs -Q, and load org-mode 2. Use this file (two lines): * <<<a>>> a-bug 3. export to HTML (C-c C-e h h) I got: Debugger entered--Lisp error: (error "Invalid search bound (wrong side of point)") re-search-forward("\\(?:[_^][-{(*+.,[:alnum:]]\\)\\|[*~=+_/][^ \n]\\|\\<\\(?:b\\(?:bdb\\|ibtex\\)\\|doi\\|elisp\\|f\\(?:ile\\(?:\\+\\(?:\\(?:emac\\|sy\\)s\\)\\)?\\|tp\\)\\|h\\(?:elp\\|ttps?\\)\\|i\\(?:d\\|nfo\\|rc\\)\\|m\\(?:ailto\\|essage\\)\\|news\\|shell\\|tel\\|w\\(?:3m\\|l\\)\\):\\|\\[\\(?:fn:\\|\\[\\|[0-9]\\{4\\}-[0-9]\\{2\\}-[0-9]\\{2\\}\\|[0-9]*\\(?:%\\|/[0-9]*\\)\\]\\)\\|@@\\|{{{\\|<\\(?:%%\\|<\\|[0-9]\\|\\(?:b\\(?:bdb\\|ibtex\\)\\|doi\\|elisp\\|f\\(?:ile\\(?:\\+\\(?:\\(?:emac\\|sy\\)s\\)\\)?\\|tp\\)\\|h\\(?:elp\\|ttps?\\)\\|i\\(?:d\\|nfo\\|rc\\)\\|m\\(?:ailto\\|essage\\)\\|news\\|shell\\|tel\\|w\\(?:3m\\|l\\)\\)\\)\\|\\$\\|\\\\\\(?:[a-zA-Z[(]\\|\\\\[ ]*$\\|_ +\\)\\|\\(?:call\\|src\\)_" 13 t) org-element--object-lex((bold code entity export-snippet footnote-reference inline-babel-call inline-src-block italic line-break latex-fragment link macro radio-target statistics-cookie strike-through subscript superscript target timestamp underline verbatim)) org-element--parse-objects(13 19 (paragraph (:begin 13 :end 19 :contents-begin 13 :contents-end 19 :post-blank 0 :post-affiliated 13)) (bold code entity export-snippet footnote-reference inline-babel-call inline-src-block italic line-break latex-fragment link macro radio-target statistics-cookie strike-through subscript superscript target timestamp underline verbatim)) org-element--parse-elements(13 19 planning nil nil nil (section (:begin 13 :end 19 :contents-begin 13 :contents-end 19 :post-blank 0 :post-affiliated 13))) org-element--parse-elements(13 19 section nil nil nil (headline (:raw-value "<<<a>>>" :begin 2 :end 19 :pre-blank 1 :contents-begin 13 :contents-end 19 :level 1 :priority nil :tags nil :todo-keyword nil :todo-type nil :post-blank 0 :footnote-section-p nil :archivedp nil :commentedp nil :post-affiliated 2 :title ((radio-target (:begin 4 :end 11 :contents-begin 7 :contents-end 8 :post-blank 0 :value "a" :parent #0) #("a" 0 1 (:parent #3))))))) org-element--parse-elements(2 19 first-section nil nil nil (org-data nil)) org-element-parse-buffer(nil nil) … It happens with one-letter radios. I found it because I had <<<R>>> and r-cran in the same file. Greetings, Daniel