Meanwhile I made a mkv from a BD with Make MKV and it had the same sync problems.
But most probably my settings must have been messed up the last few days. I uninstalled MC and reinstalled it, restored my library from a backup and I had the same problems. Then I uninstalled again, this time completely (also removing the library) and made the settings the same as before (in audio and video etc) and started from scratch, rebuilding the library. Everything plays fine now, no synchronizing problems anymore as far as I can see. Unfortunately I still don't know what has been the problem.
Btw, this is the Graph Info I get now:
Filter Graph Info:
Filter 'JRiver Audio Renderer'
CLSID: {A4002F8E-510F-442C-8AD3-F9C7B23FB394}
Host:
Input Pin 'In'
Connected to pin 'Output' of filter 'LAV Audio Decoder (auto-configured)'
Major type MEDIATYPE_Audio Sub type MEDIASUBTYPE_PCM, Format type FORMAT_WaveFormatEx
Filter 'JRiver Subtitle Renderer'
CLSID: {F74E834C-9C98-43ED-89B1-19A9DF82E774}
Host:
Input Pin 'In'
Connected to pin 'Subtitle' of filter 'LAV Splitter (auto-configured)'
Major type Unknown GUID Name: {E487EB08-6B26-4BE9-9DD3-993434D313FD} Sub type Unknown GUID Name: {04EBA53E-9330-436C-9133-553EC87031DC}, Format type Unknown GUID Name: {04EBA53E-9330-436C-9133-553EC87031DC}
Filter 'madVR'
CLSID: {E1A8B82A-32CE-4B0D-BE0D-AA68C772E423}
Host: C:\Users\Ton\AppData\Roaming\J River\Media Center 17\Plugins\madvr\madvr.ax
Input Pin 'Input'
Connected to pin 'Output' of filter 'LAV Video Decoder (auto-configured)'
Major type MEDIATYPE_Video Sub type MEDIASUBTYPE_NV12, Format type FORMAT_VideoInfo2
Filter 'LAV Video Decoder (auto-configured)'
CLSID: {EE30215D-164F-4A92-A4EB-9D4C13390F9F}
Host: C:\Users\Ton\AppData\Roaming\J River\Media Center 17\Plugins\lav\LAVVideo.ax
Input Pin 'Input'
Connected to pin 'Output' of filter 'JRiver Video Monitor'
Major type MEDIATYPE_Video Sub type Unknown GUID Name: {31435657-0000-0010-8000-00AA00389B71}, Format type FORMAT_VideoInfo2
Output Pin 'Output'
Connected to pin 'Input' of filter 'madVR'
Major type MEDIATYPE_Video Sub type MEDIASUBTYPE_NV12, Format type FORMAT_VideoInfo2
Filter 'LAV Audio Decoder (auto-configured)'
CLSID: {E8E73B6B-4CB3-44A4-BE99-4F7BCB96E491}
Host: C:\Users\Ton\AppData\Roaming\J River\Media Center 17\Plugins\lav\LAVAudio.ax
Input Pin 'Input'
Connected to pin 'Output' of filter 'JRiver Audio Monitor'
Major type MEDIATYPE_Audio Sub type Unknown GUID Name: {00002001-0000-0010-8000-00AA00389B71}, Format type FORMAT_WaveFormatEx
Output Pin 'Output'
Connected to pin 'In' of filter 'JRiver Audio Renderer'
Major type MEDIATYPE_Audio Sub type MEDIASUBTYPE_PCM, Format type FORMAT_WaveFormatEx
Filter 'JRiver Video Monitor'
CLSID: {A4207487-E7D8-406B-9882-B66370DE2492}
Host:
Input Pin 'Input'
Connected to pin 'Video' of filter 'LAV Splitter (auto-configured)'
Major type MEDIATYPE_Video Sub type Unknown GUID Name: {31435657-0000-0010-8000-00AA00389B71}, Format type FORMAT_VideoInfo2
Output Pin 'Output'
Connected to pin 'Input' of filter 'LAV Video Decoder (auto-configured)'
Major type MEDIATYPE_Video Sub type Unknown GUID Name: {31435657-0000-0010-8000-00AA00389B71}, Format type FORMAT_VideoInfo2
Filter 'JRiver Audio Monitor'
CLSID: {A4207487-E7D8-406B-9882-B66370DE2492}
Host:
Input Pin 'Input'
Connected to pin 'Audio' of filter 'LAV Splitter (auto-configured)'
Major type MEDIATYPE_Audio Sub type Unknown GUID Name: {00002001-0000-0010-8000-00AA00389B71}, Format type FORMAT_WaveFormatEx
Output Pin 'Output'
Connected to pin 'Input' of filter 'LAV Audio Decoder (auto-configured)'
Major type MEDIATYPE_Audio Sub type Unknown GUID Name: {00002001-0000-0010-8000-00AA00389B71}, Format type FORMAT_WaveFormatEx
Filter 'LAV Splitter (auto-configured)'
CLSID: {B98D13E7-55DB-4385-A33D-09FD1BA26338}
Host: C:\Users\Ton\AppData\Roaming\J River\Media Center 17\Plugins\lav\LAVSplitter.ax
Output Pin 'Video'
Connected to pin 'Input' of filter 'JRiver Video Monitor'
Major type MEDIATYPE_Video Sub type Unknown GUID Name: {31435657-0000-0010-8000-00AA00389B71}, Format type FORMAT_VideoInfo2
Output Pin 'Audio'
Connected to pin 'Input' of filter 'JRiver Audio Monitor'
Major type MEDIATYPE_Audio Sub type Unknown GUID Name: {00002001-0000-0010-8000-00AA00389B71}, Format type FORMAT_WaveFormatEx
Output Pin 'Subtitle'
Connected to pin 'In' of filter 'JRiver Subtitle Renderer'
Major type Unknown GUID Name: {E487EB08-6B26-4BE9-9DD3-993434D313FD} Sub type Unknown GUID Name: {04EBA53E-9330-436C-9133-553EC87031DC}, Format type Unknown GUID Name: {04EBA53E-9330-436C-9133-553EC87031DC}