It appears that the DeviceLog message output is truncated. This means that the assert messages get truncated and so import information about which assert failed will not appear.
It seems at least some characters from the message get dropped by the devicelog.
The message itself is correct as it is sent to the device log and the debug log from within the same function;
Device Log()
Debug Log()
This can either mean two things:
or
I found out that the device itself is probably to blame... it can not display messages > 127 characters.
workarounds;
1) split the logmessage over two lines,
2) Use alternative logging mechanism (like the debuglogger),
3) Use an Element Collection List.
Other tricks?
1) SDCard?
2) OSCAT?
Confirmed by Ingo, it is limited around 128