Hello everyone,
I encounter a quirk that I have trouble explaining and which is causing me serious problems.
And despite my research (a few sleepless nights) I can't find anything similar to this mystery.
I installed a Multiplus 2 48/3000/35 + Cerbo GX + ET112 + AC probe + 2 Pylontech (US2000C) on my PV installation (3kWp micro-inverters) to do ESS connected to the grid.
The system is in parallel with the network and the inverter (See diagram below) When the PVs produce well no problem the battery charges (even if I had to lower the charging current to 15A, but I think it is related to my problem) and the system is maintained around the grid set point .
On the other hand, as soon as the PV production drops and goes below 15A of the charging current, the system discharges the battery into the grid (50A), which causes the battery voltage to drop to the sustaint voltage (48V on pylontech) and suddenly, to compensate, it charges the batteries thoroughly from the grid.
And it alternate like that from one extreme to the other every 15 to 30 s. (below my settings). I've cut everything for now and tried a lot of combinations (including a full factory reset) but nothing still does the same behavior. (all Firmware are up to date). Can anyone help me? Thank you for your precious help. 
