"bad file descriptor" when using git mirror

**Environment:**
Buildkite agent docker image with minor customizations (node, some extra scripts, and docker configuration)
Mirror directory is mounted AWS EFS volume (effectively NFS)
AWS Graviton processors
Agent version 3.75.1

**What's happening?**
After upgrading our agent from 3.74.0 to 3.75.1, we started seeing this message (somewhat redacted):

```
2024-07-29 12:48:01 PDT | # Could not acquire lock on "/buildkite/mirrors/https---github-com-******.clonelockf" (bad file descriptor)
-- | --
  | 2024-07-29 12:48:01 PDT | ⚠️ Warning: Checkout failed! getting/updating git mirror: bad file descriptor (Attempt 1/3 Retrying in 2s)
```

This caused all checkouts to fail on the new agent version. Upon reverting to 3.74.0, the errors went away. This appears to be specific to the agent version, not our environment.