Buffer file format

### Describe the bug

I know fluentd buffers have their own binary encoding but strings which I expect to be the same in the buffer file have inconsistencies

### To Reproduce

cat --show-nonprinting buffer.b5ee47fc4ebdc5a82c9c3788851a80181.log

### Expected behavior

sky.top_tenant should be consistent in the whole file. The strings below should all be the same but they contain different non-printable characters.

The following are 3 separate examples from the cat command of the buffer file

```
sky.top_tenantM-$waveM
skyM-^AM-*top_tenantM-(identityM
sky.top_tenantM-$waveM
```

The input being passed in is: sky.top_tenant

In the same buffer file we have we have sky.top_tenant being shown differently when the input is the same

### Your Environment

```markdown
- Fluentd version: 1.15.2
- TD Agent version: N/A
- Operating system: Ubuntu
- Kernel version: 5.15.0-1022-aws
```

### Your Configuration

```apache

@type copy
@log_level info

@type elasticsearch
reconnect_on_error true
reload_on_failure true
reload_connections false
max_retry_putting_template 1
request_timeout 60s
fail_on_putting_template_retry_exceed false
slow_flush_log_threshold 100.0
@id out_es_logs-tenant_in_mono
@log_level info
log_es_400_reason true

id_key _hash
remove_keys _hash

hosts {redacted}
user "{redacted}"
password "{redacted}"
ca_file "/etc/fluentd/aaa.crt"
ssl_version TLSv1_2
ssl_verify false

index_name logs-${sky.top_tenant}-fluentd
time_key time
include_timestamp true
include_tag_key true
flatten_hashes false
flatten_hashes_separator _

# Rollover index config
rollover_index true
application_name default
index_date_pattern "now/d"
deflector_alias logs-${sky.top_tenant}-fluentd

# Index template
template_name logs-${sky.top_tenant}-fluentd
template_file /etc/fluentd/logs-template.json
customize_template {"<>":"${sky.top_tenant}"}
template_overwrite true

retry_wait 20s
retry_exponential_backoff_base 2
retry_type exponential_backoff
retry_max_interval 300s
disable_chunk_backup true
@type file
path /fluentd/es-out-logs-tenant_in_mono

flush_thread_count 8
flush_interval 5s
flush_at_shutdown true
overflow_action block
chunk_limit_size 16M
# total_limit_size is set 70% of the data disk do that 1 single out can't use more than this
total_limit_size 137G
retry_forever false

```

### Your Error Log

```shell
There are errors in the log but unsure if they are related

2022-11-25 11:21:15 +0000 [warn]: #6 [out_es_logs-tenant_in_mono] failed to flush the buffer. retry_times=4 next_retry_time=2022-11-25 1
1:26:33 +0000 chunk="5ee25623683db952a383785930d688c3" error_class=Fluent::Plugin::ElasticsearchOutput::RecoverableRequestFailure error=
"could not push logs to Elasticsearch cluster ({:host=>\"{redacted}\", :port=>9200
, :scheme=>\"https\", :user=>\"{redacted}\", :password=>\"obfuscated\"}): EOFError (EOFError)"
```

### Additional context

_No response_