Hello Gabriel,
I have a similar behavior in my DESS system. DESS - Target SOC 60%, sun, surplus PV, grid consumption - why?.
You are not alone 
So far, I could not find out, why it behaves like that. Maybe we get improvements with the new OS version 3.6x, which is still in Beta. It mentions DESS improvements: Venus OS v3.60~49 available for public testing - #96 by Maxs.
v3.60~47
Dynamic ESS
Improve how Dynamic ESS reacts when actual consumption or solar production differs from forecasted. For example when there is more solar then expected, the updated algorithm will in many cases use that extra solar power to charge the battery, even if that would exceed the planned SOC level for the current hour. Instead of feeding that excess solar back into the grid for a low price, to later have to buy it back at a higher price.
I might give it a try within the next days in combination with the new MultiPlus firmware v556.