Hello. I saved and quit the game with my Wyrmling summoned earlier today. Just now I loaded the game and re-summoned the Wyrmling, because he had 50% hp. Yet, instead of re-summoning it just summoned a second Wyrmling. And they both follow me and both fight... what Tried it out again, now I have a third Wyrmling. It seems that only one of the Wyrmlings actually attack once per turn, other just float around acting as walls. Nevermind that.
I was playing 1.07 last night and also noticed the wyrmling (and maybe other summons) dont' attack when I stealth/invis, but wanders around doing nothing. Balance maybe, but if I can can cast it on the end of my vision and walk away and let it earn me exp, I don't see how being invis would be much different.
If you have a wyrmling alive when you save, and then reload and summon another wyrmling, you get another wyrmling rather than overwriting the last one. This can be repeated ad nauseum. Don't know if it works with other pets.
It does repeat for other pets. The bug is that when you save your pet seems to lose the flag that makes the game consider it your pet. This means that it is treated like a charmed animal, so you are allowed to summon pets without removing it. If there are enemies though, unlike a pet it will target you even if it is there.