creepA.transferEnergy(creepB) throws an error:

Game.creeps['Mason'].transferEnergy(Game.creeps['Hunter']);
TypeError: Cannot read property 'structureType' of undefined at utils.defineGameObjectProperties.room.pos.name.body.my.owner.spawning.ticksToLive.carryCapacity.carry.o.fatigue.Creep.moveByPath.Creep.transferEnergy (/opt/engine/dist/game/creeps.js:384:61)

Is this an intended change with the recent downtime?

Since the update I can not create Flags via createFlag(..) or destroy structures using destroy().

Some sample output from console:

> Game.getObjectById('55f169af70bcc033713aa86e')
< [structure (extension) #55f169af70bcc033713aa86e]
> Game.getObjectById('55f169af70bcc033713aa86e').destroy();
< 0
> Game.getObjectById('55f169af70bcc033713aa86e')
< [structure (extension) #55f169af70bcc033713aa86e]

> Game.rooms.E2N3.createFlag(new RoomPosition(24, 24, 'E2N3'));
< Flag1
> Game.flags.Flag1
< undefined

When placing a new spawn it seems that no extension may exist near the selected position. On the other hand, new extensions may be constructed right next to already existing spawns.

Currently I work around this by removing extensions, placing the new spawn and then reconstructing the extensions. Please adjust the placement rules to either disallow a new extension near a spawn or allow a new spawn near an extension (I prefer the latter).

There is already another topic on this: http://support.screeps.com/hc/communities/public/questions/201412212-Multiple-Energy-Drop

After experiencing this myself several times, I thought about using this as an actual mechanic. You can see a working POC in room W1N1.

Whenever a creep ("victim") enters the holy square, he gets dropped down to 10 hp. On the next tick he is sacrificed to the energy gods. This ritual is rewarded with incredible amounts of energy.

I'll let you figure out the math behind this, but it scales quite well.

Somebody using this mechanic is pretty easy to discover, just take a look at "creep lost" on the map. But one could switch to farming keepers with this mechanic, which would be harder to detect.

So please fix. I'll leave my POC up until then, for researching purposes

Yes, that spot is closer to a source than any of the others, so that has to be the reason, thanks.

In my room (W1N1) I can't place extensions in certain spots (e. g. x:13 y:15). If I try via GUI, nothing happens. If I try via API, I get an error (-7). There is nothing special about these spots, where it doesn't work, so are there any hidden rules to where an extension can be placed? Or is it just a bug?

Right now I can't place any more extensions, because I hit the limit, just FYI.