Error PLP0000: [Errno 28] No space left on device

Issue

When I'm trying synchronize one of my capsules the specific error is present:

Name: Synchronize capsule 'capsule.example.com'
Result:  
Triggered by: admin
Execution type: Immediate
Start at: about 1 hour ago
Started at: about 1 hour ago
Ended at: N/A
Start before: -

State: paused
100% Complete
Errors:

PLP0000: [Errno 28] No space left on device: '/var/cache/pulp/reserved_resource_worker-0@capsule/cf0a5708-adc4-4c11-9d6e-1a8a13cf7b8e/nectar-ssl_ca_cert-mcEL4r'
PLP0000: [Errno 28] No space left on device: '/var/cache/pulp/reserved_resource_worker-1@capsule/959a612e-98db-4403-bd2e-371c0e7eaf42/nectar-ssl_ca_cert-9NoFnG'

But I have space on my server:

[root@capsule ~]# df -h
Filesystem                             Size  Used Avail Use% Mounted on
/dev/mapper/rootvg-root                 40G  3.8G   34G  11% /
devtmpfs                               3.9G     0  3.9G   0% /dev
tmpfs                                  3.9G   12K  3.9G   1% /dev/shm
tmpfs                                  3.9G  362M  3.5G  10% /run
tmpfs                                  3.9G     0  3.9G   0% /sys/fs/cgroup
/dev/sda1                              477M  153M  296M  35% /boot
/dev/mapper/rootvg-var                  40G  2.0G   36G   6% /var
/dev/mapper/capsule_vg-lib--pulp_lv    564G  311G  254G  56% /var/lib/pulp
/dev/mapper/capsule_vg-mongodb_lv       20G   14G  6.3G  69% /var/lib/mongodb
tmpfs                                  783M     0  783M   0% /run/user/0
tmpfs                                  783M     0  783M   0% /run/user/1046
tmpfs                                  783M     0  783M   0% /run/user/5853346
/dev/mapper/capsule_vg-cache--pulp_lv   66G   66G   20K 100% /var/cache/pulp
tmpfs                                  783M     0  783M   0% /run/user/510000