Run this line in Console several times and get different results:

> new RoomPosition(32, 40, "W12S28").lookFor("flag")
< [flag Flag24]
new RoomPosition(32, 40, "W12S28").lookFor("flag")
<

I have the flag Flag24 ontop of the link in this position. But sometimes (~ once every 5-10 ticks) lookFor cant find it.

1. Open new incognito tab (in Chrome 46.0)

2. Open screeps.com. Click Simulation. Click Custom mode

3. Open screeps console tab, write Game. Output:

ReferenceError: Game is not defined
    at _console1445359080394_0:1:191
    at eval:3:4
    at Object.c.runCode:6:7516

No errors in Browser dev tools console.

1. Type _.keys(global) in screeps console tab. Output:

global,Reflect,caches

Was it fixed?
I dont see this bug any more.

See http://screeps.wikia.com/wiki/Creep#Movement for details

And play screeps body calculator: http://codepen.io/findoff/full/RPmqOd/

for(var name in Game.creeps){
  var creep = Game.creeps[name];
  if (creep.memory.role == 'harvester') { ... }
  else if (creep.memory.role == 'builder') { ... }
  ...
}

• sight = sign

1. You can't rename creep. Usually it is easier to wait until it ages and die and born another one with the right name.
2. You can't access creep with '-' in the name that way (because it is minus operation sight in JavaScript), but you can do it like Game.creeps['B-0']
3. It is better not to use creep names in your logic. Use creep.memory instead.

I log every time findClosestByPath(exit) returns not a RoomPosition.
And constantly receive messages like these:

[16:32:24] WTF, [room W13S28 pos 46,0].findClosestByPath(exit = 1) -> [structure (extension) #5609b3d15b98a02a0fa80610]
[16:32:35] WTF, [room W13S28 pos 46,0].findClosestByPath(exit = 1) -> [structure (extension) #5609b3d15b98a02a0fa80610]
[16:33:00] WTF, [room W13S28 pos 46,0].findClosestByPath(exit = 1) -> [structure (extension) #560748bd98fe6b9220df94e2]
[16:33:05] WTF, [room W13S28 pos 46,0].findClosestByPath(exit = 1) -> [structure (extension) #560748bd98fe6b9220df94e2]
[16:33:10] WTF, [room W13S28 pos 46,0].findClosestByPath(exit = 1) -> [structure (extension) #560748bd98fe6b9220df94e2]
[16:33:15] WTF, [room W13S28 pos 46,0].findClosestByPath(exit = 1) -> [structure (extension) #5609b3d15b98a02a0fa80610]

Can you please fix this bug?

This is the same issue I think:
http://support.screeps.com/hc/communities/public/questions/201504051-pos-findClosestByPath-flags-returns-not-a-flag

And doublet queries behave that way:

Game.rooms['W12S23'].getPositionAt(49, 42).findClosestByPath(3)
Game.rooms['W12S23'].getPositionAt(49, 42).findClosestByPath(3)
[room W12S23 pos 49,42]
[room W12S23 pos 49,42]
Game.rooms['W12S23'].getPositionAt(49, 42).findClosestByPath(3)
Game.rooms['W12S23'].getPositionAt(49, 42).findClosestByPath(3)
[structure (extension) #5610f4e97232cb0022417b4c]
[structure (extension) #5610f4e97232cb0022417b4c]
Game.rooms['W12S23'].getPositionAt(49, 42).findClosestByPath(3)
Game.rooms['W12S23'].getPositionAt(49, 42).findClosestByPath(3)
[room W12S23 pos 49,42]
[room W12S23 pos 49,42]

reproduce in console:

Game.rooms['W12S23'].getPositionAt(49, 42).findClosestByPath(3)
[9:03:09] [room W12S23 pos 49,42]
Game.rooms['W12S23'].getPositionAt(49, 42).findClosestByPath(3)
[9:03:10] [structure (extension) #5612f7dcb3c550e1219a1da9]