What can be done about repeated docker build failures of docs repo?

Question

No builds have succeeded since yesterday. Latest says:

> Running with gitlab-runner 12.6.0 (ac8e767a)   on WST CI ec23033b
> Using Docker executor with image
> docker-registry.ec2-1.washingtonsquaretech.com:5000/builds/wst-buildci:latest
> ... 02:26 Pulling docker image
> docker-registry.ec2-1.washingtonsquaretech.com:5000/builds/wst-buildci:latest
> ... Using docker image
> sha256:9dad4b958eb60eafd7302c5ad05bb87bccdfe3b80edef2a22881eb79c8fe3c76
> for
> docker-registry.ec2-1.washingtonsquaretech.com:5000/builds/wst-buildci:latest
> ... Pulling docker image gitlab/gitlab-runner-helper:x86_64-ac8e767a
> ... 00:00 ERROR: Job failed (system failure): error during connect:
> Post
> https://172.31.24.149:2376/v1.25/containers/create?name=runner-ec23033b-project-236-concurrent-0-predefined-0:
> EOF (executor_docker.go:742:29s)

First one to fail said:

> warning No character metrics for ' ' in style 'Main-Regular' and mode
> 'text' warning No character metrics for ' ' in style 'Main-Regular'
> and mode 'text' warning No character metrics for ' ' in style
> 'Main-Regular' and mode 'text' warning unable to find prism language
> 'c++' for highlighting. applying generic code block success run page
> queries - 269.419s - 1421/1421 5.27/s success write out requires -
> 1.082s success Building production JavaScript and CSS bundles - 35.761s success Rewriting compilation hashes - 0.001s success Building HTML renderer - 2.051s success Building static HTML for pages - 3.667s
> - 1421/1421 387.49/s success onPostBuild - 7.637s info Done building in 332.285101143 sec Done in 333.33s. $ . scripts/publish_docker.sh
> Error response from daemon: Error processing tar file(exit status 1):
> write /.cache/json/_topics_glint-plotbuilder_.json: no space left on
> device ERROR: Job failed: exit code 1

How to troubleshoot this?