I think I have the same problem. Also some "TODO" keywords are now highlighted in some headings but it could be related.
font-lock-fontify-keywords-region: Wrong type argument: listp, org-level-1Error during redisplay: (jit-lock-function 240) signaled (wrong-type-argument listp org-level-1)
Error during redisplay: (jit-lock-function 1906) signaled (wrong-type-argument listp org-level-1)
Error during redisplay: (jit-lock-function 8102) signaled (wrong-type-argument listp org-level-1)
Error during redisplay: (jit-lock-function 9663) signaled (wrong-type-argument listp org-level-1)