Not sure if I'm the cause of this issue or not, but I thought I'd log it just in case. I've noticed that the library seems to fail to work correctly after 9ish hours (continuous - no sleep) which I believe it the timers rollover point. This isn't too much of an issue for my use case so I'm not going to debug much.

When trying to transmit a message I check ttn.busyDuration() which returns 20 every time (which I believe means it's waiting on an alarm) and trying to transmit results in a failure.