Navdata waypoint coding: ICAO code not longer than 5 characters. Any reason for that?

I’m working in a navdata addon wich will introduce all the Spanish VFR notification points into the sim as waypoints for the G10000 and all of the other avioncs.

I found that, if I give a name to the waypoint wich is longer than 5 characters, the compiler fails with the following error:
INTERNAL COMPILER ERROR: #C2024: Failed to process closing element tag near line (whatever line)!

There is any reason for that? I can insert up to 6 characters in the NXi, for example:

I need to insert up to 6 characters in order to name properly the VFR notification points like LEBBS1.