Maybe the crx/de package manager is not responding as expected due to some reason, I suggest you tail the error log while uploading a file to reveal the actual problem.You can also reveal the console log from "inspect element" to see if there are any other useful information to find your case. Take a look at this blog article,
Tailing the logs should give you the exact problem. Another suspected problem might be the docker container storage limits. The current Docker version, there is a default limitation on the Docker container storage of 10Gb. You can try to update your container storage limits here -> Overcoming Container Storage Limitation – BlazeMeter