Assistance with Vibrations on hard mount cube

#1

It seems i am encountering a high Z vibration on a 1400mm Hexacopter with 22inch props.
https://plot.dron.ee/BDzB
I have been trying to figure out solutions to solve, since as its noticable that three minutes into the flight clip0 jumps to 40 and 5 minutes in, increases to 900+
Clip1, 5 minutes in jumps to 32 and clip2 jumps to 300+
At the same time X-Y vibes peak at 30 while Z goes crazy and accelZ is pretty close to max values in many occasions.
Is there some “soft” dampening solution, since frame has been checked over and over for flex and vibrations.
The whole issue causes the HEXA to start rolling (5minutes in) at extreme angles and after about a minute it recovers and starts flight normally again.
Any assistance would be appreciated

(Upon investigation under the Cube, i found that the actual base plate has flex and in the meantime i will switch it with a 2.5mm carbon to verify if this will lower the issue, besides this structural fix, since flex is almost zero for the size, would ins_accel filtering help?)

#2

50 in 5 minutes is insignificant
It reads at 4000 x per second…

Post a high rate FFT log.