Hi, after I changed all 7 spheres, 3 months ago, I started noticing same problem as you had. Every 2 weeks pump change sound(start to sound weak), then when I check lds there is air in the system. After I do 2 times manual procedure of decompression pump start to sound and work propely.
Did you fix problem with another pump, and did you changed only pump or maybe reservoir and some pipes also? In my case mechanic also overfilled lds after changed spheres and didnt do proper decompression, so I went back to service and they took out almost half liter of lds and did decompression with lexia, but unfortunately problem keeps requiring after every few hundred kilometres.