No an expert here...but is this do to with your lipos and not enough draw from them.
What is the C rating for the lipo and the Amp draw from the ESC?
I expect a 5.5T is going to demand lots of power!
Try using different lipos.
Also what's the lipo cut-off set at on the ESC?
Like I said, I'm no expert but just giving my opinion..
Hope you sort it!
