No metrics after master slave switch

I had percona-agent running and reporting on a set of master and slave DBs. Everything was working fine, until I promoted the slaves to masters and then rejoined the old masters as a slaves. Once the switch was finished, my new masters were reporting correctly, but the slaves were not. The agents are connected, but I’m no longer getting any metrics. On one slave, the log is clean. On the other slave, I keep getting this error: write unix /var/run/mysqld/mysqld.sock: broken pipe. Why would switching roles break percona-agent? Any help is appreciated.