synths only make sound when frozen

Hi,
 
I'm using Platinum Producer. I have several projects where soft synths don't make any sound unless they're frozen. I have to thaw and re-freeze after every edit, or to change the patch.
 
It doesn't happen all the time, but it does happen most of the time. For example, I was working with D-PRo today, and all was well for a while. After an hour or two, the symptom appeared, and now it's thaw-freeze every time I want to audition a patch.
 
Has anyone here experienced this problem?
 
 

An outside chance, but does moving the volume fader on the synths midi input track (not audio output) restore sound? If so your soft synths volume is being zeroed. Go to preferences>project>midi and untick "zero controllers when playback stops".

Thanks to everyone for the replies!
 
I'm posting my system info below @ karhide's request. I'm using Sonar Platinum 2017.01 with a Focusrite Scarlett 6i6 USB interface.
 
The problem may be related to project complexity, and affects both D-Pro and Rapture. The project I'm working on (where the problem occurs) has 41 tracks. 21 Audio, 5 MIDI, the rest are instrument tracks for various soft synths. One of the synths is a drum module with 8 output channels.
 
I created a new project with 1 MIDI track, one instrument track, and 1 instance of D-Pro. That project behaves correctly.
 
Bruce, thanks for the suggestion, I'll try that in a minute and let you know.
 
Mike, I'm driving the synth from recorded midi data, I don't think input echo matters. Am I right?
 
OS Name Microsoft Windows 10 Pro
Version 10.0.14393 Build 14393
Other OS Description Not Available
OS Manufacturer Microsoft Corporation
System Name DESKTOP-DRQJSPC
System Manufacturer ASUS
System Model All Series
System Type x64-based PC
System SKU All
Processor Intel(R) Core(TM) i5-4670K CPU @ 3.40GHz, 3300 Mhz, 4 Core(s), 4 Logical Processor(s)
BIOS Version/Date American Megatrends Inc. 1207, 7/1/2013
SMBIOS Version 2.7
Embedded Controller Version 255.255
BIOS Mode Legacy
BaseBoard Manufacturer ASUSTeK COMPUTER INC.
BaseBoard Model Not Available
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Platform Role Desktop
Secure Boot State Unsupported
PCR7 Configuration Binding Not Possible
Windows Directory C:\WINDOWS
System Directory C:\WINDOWS\system32
Boot Device \Device\HarddiskVolume1
Locale United States
Hardware Abstraction Layer Version = "10.0.14393.206"
User Name DESKTOP-DRQJSPC\larry-allen
Time Zone Pacific Daylight Time
Installed Physical Memory (RAM) 8.00 GB
Total Physical Memory 7.69 GB
Available Physical Memory 4.66 GB
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Hyper-V - VM Monitor Mode Extensions Yes
Hyper-V - Second Level Address Translation Extensions Yes
Hyper-V - Virtualization Enabled in Firmware No
Hyper-V - Data Execution Protection Yes