Java SDK Subscription Refresh Causing 401 Error

I'm able to successfully create a new subscription using the Java SDK, but when the subscription attempts to refresh itself it's failing with a 401 error. Either there is a bug with the Java SDK or I'm missing something.

When the subscription is created, it starts a timer to regularly refresh itself:

https://github.com/ringcentral/ringcentral-java/blob/master/src/main/java/com/ringcentral/Subscription.java#L89

Bug when this code runs:

https://github.com/ringcentral/ringcentral-java/blob/master/src/main/java/com/ringcentral/Subscription.java#L110

This error results:

com.ringcentral.RestException: HTTP status code: 401

{

"errorCode" : "TokenInvalid",

"message" : "Token not found",

"errors" : [ {

"errorCode" : "OAU-213",

"message" : "Token not found"

} ]

}

at com.ringcentral.RestClient.request(RestClient.java:152)

at com.ringcentral.HttpClient.put(HttpClient.java:43)

at com.ringcentral.HttpClient.put(HttpClient.java:77)

at com.ringcentral.Subscription.refresh(Subscription.java:115)

at com.ringcentral.Subscription$2.run(Subscription.java:94)

at java.util.TimerThread.mainLoop(Timer.java:555)

at java.util.TimerThread.run(Timer.java:505)

Am I doing something wrong or is this an issue with the SDK?