...Okay, I've managed to figure out what it is, and it is
not a bug. Here is how it works.
When you place down a group of shield rechargers and some shield capacitors, then have shield rechargers or capacitors selected in your building hotbar, you should see this (if not, relog/restart the game client):
That bubble is your shield radius. No, it is
NOT A BUBBLE SHIELD, but it indicates the maximum radius in which the shields from your generator will fill capacitors and protect blocks. Blocks outside that radius will not be shielded. Larger generator groups have a larger radius.
Those pink line things are two arrows, showing that the shield capacitor groups are associated with that shield generator module.
If you try to put a shield generator group in the radius of another group, what you get is this:
This means that the second shield generator is not active. Note how the arrows for the shield capacitors still point towards the first group of shield generators, and not the second. If two or more generators exist inside each other's effect area, only the largest and most powerful one will be active. If the areas overlap but the generators are only within their own bubble, both shielding areas will work, but the larger group seems to take precedence in the overlap area.
(Don't quote me on this, as it may not be correct.)
Again, as apparently this is a common misconception,
these are not bubble shields. Projectiles travelling into the bubble will not be stopped by the shields until they hit a block inside the radius.
