Not really sure what else to try. You could try adding the following to your connection string in web.config for the clientapi to try and close connections faster.
ConnectionIdleTimeout=5
<add name="toems" connectionString="server=localhost;port=3306;database=theopenem;Uid=root;Pwd=password;Allow User Variables=True; ConnectionIdleTimeout=5;" providerName="MySql.Data.MySqlClient" />
or disable pooling
Pooling=false
<add name="toems" connectionString="server=localhost;port=3306;database=theopenem;Uid=root;Pwd=password;Allow User Variables=True; Pooling=false;" providerName="MySql.Data.MySqlClient" />