No I dont get it! Because what Im trying to tell you is, using PI's from others setup doesnt always work. Every setup differs. Its not just about being same size or orientation. Now Im even skeptic about your tuning session. And the values you claim to use is very low.

Then you talk about increasing it to '250'. WHICH ONE? Is it P or I,limits or gains? Is it self level or ail/ele/rud PI values?

Anyways as far as I can see its bad pids or bad sensor data/board (doubtful), and there is nothing more I can suggest other than increasing P of 'self level' till the time you see oscillations as in the video shown in my earlier post, and then decrease it a bit until those oscillations go. That should get your quad flying if you havent messed with the PI values of ail/ele from default. 

OR

Reset board in menu Or reflash firmware which will get you back to default values which you started with!

.. umm ok i couldn't explain the PI values.. ill probably post the values i had and have now.

ONE QUESTION Still remains which really perplexes me .. WHY .. WHY al of a sudden when there was no change to the system ??

PI Tuning i get it, ill tweak it again , the question is why did it suddenly crap out :/

You should always explain about your settings and setup in detail when you are seeking help for an issue, so as to find the issue easily without doing too much circus. It just saves the trouble.

Since you say you didnt change anything in your system and if reverting back to default or previous or working PI's settle your issue, then one thing is sure that the flight characteristics displayed in your video was the result of weak pid's and they dont change by themselves as far as i know.

OR

Somehow your board keeps forgetting settings such as the acc issue, due to a damage,bad firmware flash, noisy power supply to board etc. I dont think its acc sensor failure because when it fails it does so spectacularly if in flight!