Marking a task sometimes (very rarely) puts it at the end of the previous line

[dsowen]

Org Mode also uses overlays in the agenda buffer. It can do this to hide tasks that it considers blocked. An example would be this outline:

* TODO Task
** TODO Subtask

"Task" would be inserted into the agenda buffer, but hidden with an overlay. Additionally, it will miss most of the other text properties that Org uses for visible tasks.

The following buffer-wide properties are set:

name	value
org-agenda-type	todo
org-last-args	nil
org-redo-cmd	(org-todo-list ...)
org-series-cmd	nil

The following properties are set for the task in an overlay:

name	value
invisible	t
org-type	org-blocked-todo

A normal task looks like this (not in an overlay):

name	value
breadcrumbs	nil
done-face	org-agenda-done
dotime	t
duration	nil
extra	""
face	nil
format	...
help-echo	...
level	" "
mouse-face	highlight
org-agenda-type	todo
org-category	"goals"
org-complex-heading-regexp	...
org-hd-marker	...
org-highest-priority	65
org-last-args	nil
org-lowest-priority	67
org-marker	...
org-not-done-regexp	"\\(NEXT\\|TODO\\|WAIT\\)"
org-redo-cmd	...
org-series-cmd	nil
org-todo-regexp	"\\(DONE\\|NEXT\\|TODO\\|WAIT\\)"
priority	1
tags	nil
time	""
time-of-day	nil
todo-state	...
ts-date	nil
txt	...
type	"todo"

These blocked tasks with only overlay properties confuse the code that looks for tasks preceding a marked task.