This is due to the [Link Removed] encoded UFunction object name passing through UHT into the boilerplate code (*.gen.cpp) that gets generated from the nativized Blueprint's C++ header file.
The issue also occurs when packaging Switch, Linux and iOS targets (when nativization is turned on).
The suggested workaround for 4.18.0 (and prior) is not to use non-ASCII characters in Blueprint Function/Graph names. Variable names, however, should be clear to use non-ASCII characters in 4.18.0 only, as versions prior to 4.18.0 also do not support non-ASCII characters in new Blueprint variable names.
Head over to the existing Questions & Answers thread and let us know what's up.