Looks like the game tracks a whole bunch of variables and the system goes teats up if something prods and upsets it.
I've had a raider attack which came from an unexpected direction at a province I've only just set up.
It was pretty satisfying as they burnt a good bunch of the buildings before troops arrived to mop them up shortly afterwards.
Shit got rebuilt pretty fast, but the province kept struggling with all sorts of shit - a bunch of folks got permanently tagged
as homeless (despite there being more than enough housing), and they kept losing the oxen (despite there being a bunch of sheds and hitching posts),
which is sort of a big deal in the early game, cause no ox means no logging and no construction.
And it can really screw your over since there's no easy way to get one if you don't have the 20 shekels to fork out on it.
I've also learned the hard way that archers aren't don't do much in terms of damage. Two 25-man units let off quite a few volleys at mostly unarmored raiders and it didn't inflict even one casualty.
They also fold immediately when charged at. What they can do is divide the enemy force as the AI is really dumb and will go chasing them through the woods,
so that the rest of the guys got a bit more evenly matched - 4 groups of raiders x 18 guys vs. 50 archers, 20 spearmen and 16 retinue on my end.
This was the biggest fight I've gotten into in the beta thus far (not counting the enemy duke who fields a few mercenary units, it needs a bit more buildup until you can take it on).
I'm only mentioning this so that guys who want a "better" Total War set their expectations straight. While the system looks fairly detailed,
what you're looking at are 100 vs 100 man skirmishes. There's no cavalry, so using archers for skirmishing is basically the height of tactics you'll see.
Other than this it's just the simple anvil and hammer - spearwall braces and takes the charge, men-at-arms flank and charge.
Recent patch notes say it's being fixed (and archers are also getting a damage buff), as well as, thankfully, the food distribution system which is all black magic ATM.
So here's hoping for an update of the official branch sometime soon, because it can get pretty annoying at the moment
EDIT:
Also, I only just noticed that there are quite a few mods. Mostly value tweaks, crests and object replacements.
https://www.nexusmods.com/manorlords/mods/