I got the following warning in MapGuide log file:
Warning: An exception occurred in FDO component.
Zeichenfolge ist kein gültiger Ausdruck.
- MgStylizationUtil.ExceptionTrap() line 231 file SE_ExpressionBase.cpp
The message means "string is invalid expression".
In my case it seems the issue is related to text label style. The text label was originally published using MTEXT as style. Later on - due to a bug in MapGuide - I changed the text style to TEXT. But since I changed TEXT back to MTEXT the message doesn't appear in the log files anymore.
Autodesk Infrastructure MapServer 2017