"ER_DUP_ENTRY: Duplicate entry" when doing updateCheck

[w000xj]

i ran into a issue which #30 mentioned before, here is the error:

error making update check [Object: null prototype] {
< deploymentKey: 'smtaTujlkHTBvFHiqZUYGHJcUBWzUNY*******',
< appVersion: '3.1.0',
< packageHash:
< '4c282a0f753143ce313234c5147bfbc776e521c2cb357315d07a17d3752053b6',
< isCompanion: '',
< label: 'v53',
< clientUniqueId: 'de598acdaf63a239' } ER_DUP_ENTRY: Duplicate entry 'd7cbfa0f2e1635e91c47e19d534d298d4d8ee98ce0703a26ecffe26fd4f20a56' for key 'PRIMARY'

i'm sure it is caused by the "upload" method of electrode-ota-server-fileservice-upload

we have six servers deployed in our production environment, each connected to same database, and use pm2 to start the server, here is the pm2 config
{ ...
env_production: {
NODE_ENV: 'production',
},
instances: "6",
exec_mode: "cluster",
min_uptime: "60s",
max_restarts: 30,
max_memory_restart: "800M",
autorestart: true,
out_file: './logs/out.log',
//out_file: 'NULL',
error_file: './logs/err.log',
merge_logs: true
.....
}
the version we use is 4.6.8
i wonder if it is the proper way to set up and use electrode-ota-server?