CI global cache not writable anymore since a few hours on gitlab.com

Summary

On gitlab.com, CI global cache is not writable anymore, although same commit worked 24hours ago.
Now, when I relaunch CI jobs that worked yesterday, they're not working anymore

Steps to reproduce / Example Project

Try run the CI of this project that I created specifically for this bug here: https://gitlab.com/statnmap/ci-cache-failed

Below is my .gitlab-ci.yml file.

image: rocker/geospatial

variables:
  R_LIBS_USER: "ci/lib"

cache:
  key: global-cache
  paths:
      - ci/lib/

stages:
  - build

building:
  stage: build
  script:
    - mkdir -p $R_LIBS_USER
    # - apt update -qq && apt install -y libgdal-dev libproj-dev libgeos-dev libudunits2-dev libnode-dev libcairo2-dev libnetcdf-dev
    - Rscript -e '.libPaths(c(Sys.getenv("R_LIBS_USER"), .libPaths()));remotes::install_deps(dependencies = TRUE, lib = Sys.getenv("R_LIBS_USER"))'
    - Rscript -e '.libPaths(c(Sys.getenv("R_LIBS_USER"), .libPaths()));remotes::install_cran(c("pkgdown", "DT"), lib = Sys.getenv("R_LIBS_USER"))'
    - Rscript -e '.libPaths(c(Sys.getenv("R_LIBS_USER"), .libPaths()));devtools::check()'

What is the current bug behavior?

R package are supposed to be stored in the "ci/lib" path. But I get the following message indicating that the directory is not writable:

(converted from warning) 'lib = "/builds/statnmap/ci-cache-failed/ci/lib:/usr/local/lib/R/site-library:/usr/local/lib/R/library"' is not writable

What is the expected correct behavior?

24 hours ago this worked correctly, and now this does not work anymore.
Working correctly means that any directory created using cache was writable.

Results of GitLab environment info

Failed on

Running with gitlab-runner 13.2.0-rc2 (45f2b4ec)
  on docker-auto-scale ed2dce3a

but passed when it was

Running with gitlab-runner 13.2.0-rc2 (45f2b4ec)
  on docker-auto-scale 72989761

Results of GitLab application Check

I can not check, I am using gitlab.com