Small number of job traces disappeared after upgrade

Description

Updating from 10.5.8 to 10.8.2, made job traces that were created in the same time span (9 days) disappear from both the trace directory and does not exist as an artifacts file.

Also found some traces that do display a the trace view (black screen), but it is empty. When clicking on the button to display the raw trace we get a 500 error:

Errno::ENOENT (No such file or directory @ rb_sysopen - /gitlab/gitlab-artifacts/10/26/102624ac0a714fa26aa0f8569b1aa0f0f80c4b34de420d2bb9e46b3dfdbec039/2018_05_31/480896/937
3/job.log):

app/uploaders/job_artifact_uploader.rb:21:in `initialize'
app/uploaders/job_artifact_uploader.rb:21:in `open'
app/uploaders/job_artifact_uploader.rb:21:in `open'
app/models/ci/job_artifact.rb:23:in `open'
lib/gitlab/ci/trace.rb:63:in `block in read'
lib/gitlab/ci/trace/stream.rb:18:in `initialize'

The trace does appear to exist in in the old trace directory

Artifacts object store is not enabled: