After two weeks of testing after purchase of CS757 I find there is an issue with the VNAV function. I have previously used PMDG747, LD767 and another company 737PIC who all have the same type of FMC and they never have any kind of this issue.

Many times the LEG page show wrong speed/altitude. At cruise the ALT is correct but the speed is wrong. Example from yesterday, FMC show 255/FL340 for all waypoints after reaching cruise altitude. My speed was really .776/FL340. VNAV page show correct speed .776. No decent calculation, only RW30 at KMIA show 170/20. Last point 8nm from RW show 255/FL340!!!. Then I have to do some calculation myself and bring the plane down with FL CH and lower speed restrictions as I decent. Sometimes also last point (arrival RW) shows cruise speed/alt. LNAV works fine though.

I read all the time here "read the tutorial". I have done that and I have hundreds of hours using FMC in PMDG747/LD767/Wilco737PIC and NEVER had any kind of problem with VNAV. Even changing STAR and landing RW according to wind never cause any problem for the FMCs calculation of speed/alt during approach.

There are no issue with the AIRAC from navigraph as all of my add-on aircrafts use the same, now using 1101. Every time I get a new AIRAC all add-ons are upgraded. Only the CS757 give me wrong calculations. The FMCs of the other aircrafts work fine with 1101.

Hope this issue will be corrected with the ver4.5 upgrade.