FYI, I had to change the format of resources, to include the resource hash, which avoids loading duplicates resources. Cf https://github.com/edx-solutions/jquery-xblock/commit/1f509cf4298ddb46bdcbb82f3d1ec4e65dd4d1ec and https://github.com/edx-solutions/jquery-xblock/commit/50e9a57e40aa51f08a4bf373240636ee4f6bd282.