I was experiencing a need to prioritise everything to 9 to have any chance of dupes responding. Turned out that delivering fertiliser to planter boxes takes precedence, and with 6 fertiliser makers constantly dropping the stuff on the ground, no one would do anything else until the power ran out, freeing dupes up for other tasks... like making power, and so it went on. Couldn't find anything that was labeled as priority 9 involved in the process but thats what was happening. Ended up using an airlock to limit access as a work around.
Make enough planter boxes with blossoms and make a good number of fertiliser makers. Was enough plants to support ~25 dupes btw.