I have MIME encoded filename in Content-Disposition header like "=?UTF-8?Q?Invoice_4.png?="
ApiClient does not decode it before sanitizing and fails on temporary file creation.

if (matcher.find()) { filename = sanitizeFilename(matcher.group(1)); }

ApiClient.prepareDownloadFile must decode filename!

<dependency> <groupId>com.sun.mail</groupId> <artifactId>javax.mail</artifactId> <version>1.6.2</version> </dependency> 

filename = sanitizeFilename(MimeUtility.decodeText(matcher.group(1)));

This solution works fine!