I have a 5kw quattro and it has always worked perfectly on our 600Ah wet lead acid traction battery set*. I just installed a new set of solar panels (660w worth) and a 100-50 smart solar regulator. The batteries were fully charged and on float from the Quattro. I set the MPPT to the same parameters as the Quattro but the charge went to bulk and stayed there all day with the batteries bubbling away. It never reduced the charge.
*Last year I had the same set up but fed the output from the solar charger into the solar socket on the quattro and that worked fine though I do not know if the quattro was regulating a regulated current (if you see what I mean) I am going to increase the number of panels and as I do not know how much the quattro socket can take I wired them as per your diagram to the battery positive and shunt of the BMV712.
As the batteries behave perfectly on the quattro alone I assume there are no problems there.