SLF4J is going to think all arguments after the message are meant to be inserted in the the string, rather than seeing the last one as a throwable. Can either manually call the MessageFormatter.format method like we did for a warning elsewhere in the ServicePool:
```java
LOG.warn(MessageFormatter.format("Error returning end point to cache. End point ID: {}",
    endPoint.getId()).getMessage(), e);
```

Or, since there's no complicated formatting, could just do regular concatenation:
```java
LOG.info("Retriable exception from end point ID: " + endPoint.getId(), e);
```