Problems with 737 Serv.Upd. 1.3 (EGLL to EGLL)

Hi PMDG,after installing 1.3 service update I've noticed a strange behaviour of 737 during descent and approach.The fligt plan is: from EGLL 09R via DET SID, via BIG STAR, to 09R ILS approach.From FL120, set as cruise alt, with alt set to 2500 feet before reaching T/D point, the 737 starts descending FROM 12000 feet (after T/D) but does not descend under about 11000 feet (VNAV and LNAV on), consequently arrives to ILS alignment at about 9000 feet of altitude. Before installing 1.3 everithing worked well.Andrea