When walking in a counter-clockwise direction, the tax collector in the picture below doesn't make the whole loop--on two of his walks he disappears and on the other one he turns back! (and then disappears)

If you have described the entire road network, on the 3 walks he starts in the counterclockwise direction he should disappear each time (on the plaza tile), with no turning back.

If you didn't describe the entire road network (perhaps some more above or to the right), then he might follow a strange path after walking 35 tiles (including turning around or going off the road) and then disappear.

I thought he would always take the shortest path and get to his building on his way back.

Shortest path to what?

Why wouldn't he do it?

He should behave as a tax collector behaves, which is to disappear after walking 35 tiles if a gatehouse prevents him from walking 35 tiles toward his "walk target" that is less than 36 tiles away, or to follow a "strange" path (possibly including walking off the road) after 35 tiles and then disappear if a gatehouse prevents him from walking 35 tiles toward his "walk target" that is more than 35 tiles away. (If you don't know what a "walk target" is, I don't have time to describe it now.)

I also noted that if I replace the garden tile with road, then tax collector will start his walks on it, while others will not (assuming north is upper left).

If "others" means the citizen from the forum or walkers from a 2x2 building other than the forum, then that is correct.

[This message has been edited by Brugle (edited 03-28-2013 @ 11:20 AM).]

If you didn't describe the entire road network (perhaps some more above or to the right)...

You are exactly right, there were roads above and to the right.

Shortest path to what?

..., which is to disappear after walking 35 tiles if a gatehouse prevents him from walking 35 tiles toward his "walk target"

Is it correct then that every time "shorting due to blockage" occurs, the walker will disappear after walking his default walk length? I thought there would be a returning home part where the walker chooses the shortest path to his home building and goes there in the destination mode.

EDIT:

..., or to follow a "strange" path (possibly including walking off the road) after 35 tiles and then disappear if a gatehouse prevents him from walking 35 tiles toward his "walk target" that is more than 35 tiles away.

I counted where his walk target is for the "strange" walk, and it indeed falls on connected tile which is more than 35 tiles away. So there is both shortening by blockage and by distance, which leads to this confusing turn on the plaza tile.

Thank you, Brugle. Now it's much clearer. I was very surprised that in my recent city I had to constantly reshuffle buildings in gatehouse blocks to ensure that everybody makes the loop.

[This message has been edited by equi (edited 03-28-2013 @ 02:51 PM).]

Is it correct then that every time "shorting due to blockage" occurs, the walker will disappear after walking his default walk length?

That is true for tax collectors and engineers and entertainers, although the walker may walk a "strange" path before disappearing if he is also blocked by distance. I assume that the "strange" path of those C3 walkers is identical to that of Pharaoh walkers, which are described in reply #17 of Walkers and teleporters from pavilions.

I thought there would be a returning home part where the walker chooses the shortest path to his home building and goes there in the destination mode.

That is true for many random walkers "shorted due to blockage", but not for the walkers listed above or for school children.

Thank you Brugle, now it's all completely clear to me.
It's a very beautiful find that the "confused" part of the walk is traveling in the directions to the walk target tile as if the walker made his default walk to it through blockage.