I have had many batteries that act like yours, they were old and tired. (like me)
Mine also act like they take a full charge, but they won't deliver it.
Those batteries charge at 300 ma, but then have to put out 1.6 amps to fly the mSR
I put an amp-meter inline on my mSR to measure the true load.
As a battery ages or just decides to quit, there is a factor called internal resistance that starts to climb. If it wasn't for IR our batteries could deliver a unlimited current until they were discharged.
Batteries with a lower IR will have a higher C or amps, ability ( there are other factors involved in the final C rating)
After you fly for 30 seconds, that darn IR is dropping your output voltage, and the mSR lands, then after a little rest, the voltage comes back up a little and you can fly again probably for a shorter time.
I bought 10 batteries from HobbyKing, and they ALL did the same as yours, the originals were better. My best ones are 160ma from Hyperion, I have had flights over 8 minutes with them, and I think somehow the mSR flys smoother with them.
Try a new good battery like the Hyperion, and let me know what happens.
The mSR must be the toughest thing flying, I crashed mine about a 100 times trying to fly inside my house.