Effectiveness of vibrating bottom of Flexilo Okofen?

[yafos]

Hello everybody
We have, since 2 years, an Okofen boiler powered by suction from a textile silo S2819R to flat vibrating.
At the end of last season, the silo was never able to empty itself completely ... And we had to help the pellets to descend by tapping on the canvas. There were therefore a few kilos of pellets left on the next filling. For 2 to three months, I noticed that the filling pipe, in suction, was less "filled" than before and that the filling lasted much longer.
At the end of this season, the boiler has even more trouble to empty, suction sometimes runs empty before I hit the web! It seems to me that the vibrating floor is very discreet and even asks me if it is effective.
Does anyone have any experience on this subject and who can bring me some lights?