Synapse finds most, but not all files and opens some of them, but most not.

[Alex]

I'm using synapse 0.2.99.2 on Ubuntu 16.10 with the Cinnamon Desktop.

So far, the synapse launcher works fine. Launching applications works flawless.
However, when I search for files, only some filetypes are opened with their associated application.
Others are found, but not opened. Sometimes all are found, but only some of them opens.
When I search&navigate with the nemo file manager, I experience no problems.

Examples:
ODT document file: All are displayed, some in LibreOffice. Files on mounted volumes seem to fail here.
PNG or JPEG file: All are displayed (with thumbnail), none opens.
WEBM video file: All are displayed with thumbnail, all open in video player.
FLV/AVI/MP4 video file: All are displayed (with thumbnail), none open.
TXT file: Some are displayed, opens with editor. Files on mounted volumes seem to fail here.
XCF (Gimp) files: All are displayed, some open, some don't. But all are in /home/ subfolders.
CBZ (comic) file: All are displayed, opens with evince.

I've looked through all options and have no idea how to affect this behavior.

Hope someone has a clue what is going on with synapse and how I can find out more.

Thanks.