Transcribe Custom Vocabulary German Validation error: Your custom vocabulary file contains one or more unsupported characters

When creating a new custom vocabulary as a table I get the following error message: Validation error: Your custom vocabulary file contains one or more unsupported characters ("e", "i", "ː") in the IPA column on line 6. Supported characters are listed in the Developer Guide (https://docs.aws.amazon.com/transcribe/latest/dg/charsets.html). Remove the unsupported characters and try your request again. The first line contains (as the documentation states) Phrase[TAB]SoundsLike[TAB]IPA[TAB]DisplayAs the line in question: Pandemie[TAB][TAB]pandemiː[TAB]Pandemie

Note that the last two characters in the IPA column are copied directly from the https://docs.aws.amazon.com/transcribe/latest/dg/charsets.html?icmpid=docs_console_unmapped#char-german documentation... The file is encoded in UTF-8 with LF as EOL.