Workaround for the issue found while typing, definitely a bug, but thankfully it's relatively easy to get around. Please see the bottom line.

Modlist (in order):
HugsLib
Jecs Tools
RoM - Vampires
EdB prepare carefully
SetUp Camp
[RF] Basic Bridges A17
[RF] Smooth stone walls A17
Xeva's RimHair
Hand Me That Brick
Defensive Positions
Stack Merger
EPOE (prosthetics mod)
Turret Collection
RimRoads
Efficient Light
Harvest Everything

First off, fantastic mod, I've had a great experience with it and this is the only game-breaking bug I've found so far, and it's not even that gamebreaking.

So, I've just completed my first year, I have a 10th Gen Lasombra vampire who refuses to do anything apart from rest, at least without me manually forcing them.

I have no other vampires, and no other colonists are experiencing the same issue.

The issue occurred immediately after I installed, then removed, eye patches to regenerate scarred eyes. The regeneration happened without issue, my character's eyes are 100%. I've never seen a colonist stick on 'Standing' before, and this happened immediately after the surgery.

The action was vanilla, to remove the eyes I installed eye patches (though they were crafted at the EPOE simple prosthetics bench I'm fairly sure they're available vanilla), then removed the eye patches to leave the vampire eyeless, then regenerated the eyes.

The vampire can be forced to work on something, but as it isn't automatically picking up new jobs this requires a lot of management. Also, the vampire is severely joy-deprived with a -20 mood buff and absolutely refuses to do anything to give joy either. They DO sleep however.

To resolve the issue I have tried (unsuccessfully):

Re-ordering Vampire + Jecs tools in the mod list
Giving the vampire an injury and allowing them to heal naturally in the hospital
Removing all work priorities then re-enabling one-by-one to see if it was a specific job, it isn't
Having the vampire incapacitated through injury, then healing naturally
Casting all abilities
Entering Torpor in their coffing
Drafting/undrafting
Forming a caravan with the vampire then returning them to the colony

None of the above worked, however while typing this bug report, due to a lack of joy, the Vampire had a mental break (food binge, lol!). Once the mental break was complete, the vampire then started working normally again (phew).

So if anyone has the same, lock them in your corpse disposal room for a day or two or something, as a mental break seems to 'reset' them.

Edit - While the above has worked around the issue, a few days later this randomly occurred again in the middle of mining. Nothing to do with surgery or healing this time, but I think now that this issue has occurred it will randomly re-occur.

I've had previous playthroughs where rather than repair the eyes through the eyepatch method, I harvested them from prisoners and installed them. Those playthroughs didn't result in these issues so I recommend others harvest and replace eyes and just use the vamp regen for everything else.