sun.util.PropertyResourceBundleCharset$PropertiesFileDecoder decodeLoop
INFO: Invalid or unmappable UTF-8 sequence detected. Switching encoding from UTF-8 to ISO-8859-1

INFO is enabled by default. This seems to be the implementation detail that attempts to decode with UTF-8 first and fall back to ISO-8859-1. The log message may be intended to be TRACE/DEBUG message (FINE/FINER in java.util.logging.Level)

It's currently using PlatformLogger. It should consider using System.Logger.