Still problems with FMC and database?

Hi everybody!I am a new user of the PMDG 737 and really enthusiastic about the model and the cockpit displays. Great work there! What causes many problems for me during flying is the FMC. Though I installed the SID/STAR database and the navdatabase and I am able to select SIDs for every desired airport I am not able to select any STAR. The Approach/STAR page will just be empty on every airport.Furthermore, the FMC calculates crossing levels for some of the waypoints during climb, which do not correspond to the normal climb profile, and therefore VNAV disconnects after some time because it is not able to reach these levels (already climbed above it). In connection with this problem, there is also another one: When VNAV disconnects, no substitute pitch mode is engaged, so that the pitch of the airplane is uncontrolled if you do not select a new pitch mode by yourself immediately. I am not a real life pilot, but I cannot imagine that this could happen on a real 737. Are these problems of general nature? If yes, are there attempts to fix them? It would really be great if also the FMC and VNAV worked accurately, because then the whole thing would have no disadvantage!!!Thanks for your help!Jan Fr