TIMEOUT while waiting for operation to complete

We are currently unable to release our projects with large artifacts (the release process works for our smaller repos).

For example, the release:perform step for our killbill-platform-* artifacts fails with the following error:

...
Uploading: https://oss.sonatype.org:443/service/local/staging/deployByRepositoryId/orgkill-bill-1084/org/kill-bill/billing/killbill-platform-base/0.0.3/killbill-platform-base-0.0.3-javadoc.jar
Uploaded: https://oss.sonatype.org:443/service/local/staging/deployByRepositoryId/orgkill-bill-1084/org/kill-bill/billing/killbill-platform-base/0.0.3/killbill-platform-base-0.0.3-javadoc.jar (58 KB at 235.3 KB/sec)
[INFO] * Upload of locally staged artifacts finished.
[INFO] * Closing staging repository with ID "orgkill-bill-1084".

Waiting for operation to complete......................................................................................................
[WARNING] TIMEOUT

[ERROR] Rule failure while trying to close staging repository with ID "orgkill-bill-1084".
[ERROR]
[ERROR] Nexus Staging Rules Failure Report
[ERROR] ==================================
[ERROR]
[ERROR]
[ERROR] Cleaning up local stage directory after a Rule failure during close of staging repositories: []
[ERROR] * Deleting context 3b1321cddb50d0.properties
[ERROR] Cleaning up remote stage repositories after a Rule failure during close of staging repositories: []
[ERROR] * Dropping failed staging repository with ID "orgkill-bill-1084" (Rule failure during close of staging repositories: []).

Waiting for operation to complete.....

[ERROR] Remote staging finished with a failure: Staging rules failure!

Our largest artifact is 294M (killbill-platform-server-0.0.3-jar-with-dependencies.war). Could the size be causing the issue? It looks like the upload goes through though, but the validation stage fails.

We already tried to break up our repos into smaller ones (fewer artifacts to release at once), but it didn't help. What are our options?