IIIF manifest issue after upgrade to 8.3

[Mohana SP]

[Cross-posted]

We recently upgraded to 8.3 from 8.2 and noticed our IIIF viewer stopped working. We are using Cantaloupe as the image server. We had no issues in 8.2. We are specifically getting a 500 error for the manifest endpoint (e.g. https://example.org/server/iiif/item-uuid/manifest).

Tim has pointed out that no changes have been made in the IIIF integration in 8.3 so we don't really know why it's happening.

Has anyone encountered a similar issue? Any thoughts and suggestions are welcome. Thank you!

The specific log messages we get are:

2026-01-16 15:19:07,177 ERROR unknown 7b622ca6-b90e-40bf-8e4f-824266d9a760 org.dspace.app.rest.exception.DSpaceApiExceptionControllerAdvice @ An exception has occurred (status:500)
jakarta.servlet.ServletException: Handler dispatch failed: java.lang.NoClassDefFoundError: Could not initialize class de.digitalcollections.iiif.model.MimeType
        at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1104)

Caused by: java.lang.NoClassDefFoundError: Could not initialize class de.digitalcollections.iiif.model.MimeType
        at de.digitalcollections.iiif.model.ImageContent.<init>(ImageContent.java:36)
        at org.dspace.app.iiif.model.generator.ImageContentGenerator.<init>(ImageContentGenerator.java:29)
        at org.dspace.app.iiif.service.ManifestService.setLogoContainer(ManifestService.java:302)

Caused by: java.lang.ExceptionInInitializerError: Exception java.lang.IllegalStateException: Duplicate key application/gzip (attempted merging values application/gzip and application/gzip) [in thread "ajp-nio-127.0.0.1-8009-exec-8"]
        at java.base/java.util.stream.Collectors.duplicateKeyException(Collectors.java:135)
        at java.base/java.util.stream.Collectors.lambda$uniqKeysMapAccumulator$1(Collectors.java:182)
        at java.base/java.util.stream.ReduceOps$3ReducingSink.accept(ReduceOps.java:169)