Seeing as this "bug report" has devolved into a balance discussion, I'll add my two cents.
First on the "bug"
That can happen if your game has a lot of weapon particles on screen. Sins is programmed to only display a certain number of particles at once to prevent game lag. This can cause particles to be unloaded, which unfortunately includes the blue Eradica titan effect when unyielding will triggers, rendering it invisible. You can increase the limit in the rebellion.user.setting file if you want to reduce the chances of this happening.
As a software programmer, that screams that this ability needs to be changed. If the default installation of Sins has the strong potential to reliably reproduce this, due to a fundamental limitation of the engine; it should be reworked to be different. I'm sure most of us have already modified this file (I have) and I still occasionally see this behavior.
Now on balance
I completely agree with Riddle on this. The ability is VERY good, in my opinion too good. This titan is nearly impossible to kill in it's own culture after upgrades [which for the record I'm ok with]
What I'm not ok with is that your reward for finally killing this thing and it's massively synergistic support fleet is that you get a choice. You can retreat two or three phase jumps giving your enemy plenty of time [4 mins] to easily pump a new support fleet that will easily clean up whatever fleet you may have left [which by this point your fleet has no AM to combat their new support fleet which does]
I'm not a balance person, so I don't know exactly how to make it feel powerful and still balanced enough to not be this.
There's a few options I see and that I think is fair.
1. The ability no longer makes it invincible. It instead fully restores shields and gives half hull strength (or whatever) plus a decent armor bonus (plus it's current stats on weapon cooldown and am regen)
2. It remains exactly as is but no phase jump ability [thus less running from it and burning up your AM on jumps] Makes it very defensive as I feel it should be. Perhaps include the ability to phasejump within your culture (essentially giving you one offensive jump assuming the engine allows that)
3. [more out there idea] on death you can re spawn the titan anywhere in your culture (Thinking of you deliverance engine
) I can think of many awesome uses for this... and strangely none of them seem as broken as the ability seems now. NOTE: does not cost money, crystal, or metal but does have a 4 minute timer as is now. Can be used very defensively as well as offensively in this situation.