This was quite a thorough review on the stabilization on the GX80. It looks like a combination of OIS+IBIS+E-stab with large movements leads to extreme "torsional" jello-ing, something like how the first few M43 bodies behaved during the majority of camera movement.
There could be a fix for his sideways shifting issue if he uses mega OIS lenses that don't suffer from the jitter problem, the 12-32 pancake is known for jittering too.