TC Octave top bracing

I have a 12 year old Johnson Octave (it looks like a TC Octave clone) and the top
is sinking. It is 3/16" lower in the middle by the bridge than it is on the rim of the body.

Since it's a TC clone I was wondering if anybody knows how they are braced.
I have to get an inspection mirror so I can try to see what is going on.

Any ideas what to look for?

Thanks

My Fender-branded octave mandolin, similar to yours, was x-braced if I recall correctly.

I have an old Octave mandolin with a similar issue, the top is sunk about 3/16 “ but it seems stable, still playing well and sounds good.
It’s not quite as nice to look at as it was but , I wonder if it’s worth the hassle to take off the top and re do the bracing