In a recent build a crash was fixed which required that newly created objects don't really "fully exist" until the next event tick. You can use them in the same event that created them, but the next events won't treat them as existing until the next tick. It's a bit of an annoying quirk but it seems it's the way the engine has to work, in order to avoid other crashes in the event engine that have been reported. In this case, the 'For each' subevent to the start of layout event will not consider the tanks created in the same tick, but the 'for 1 to 8' loop will. As Linkman pointed out, you can do everything in the same event anyway.
As a side, you don't need any of the for-each loops in the 'Pick tank' groups. The conditions work like that normally.