Also, unlock before calling Act.

This was suggested in a comment for #3588 and seems to work fine without stalls.

roomserver/internal/input/input.go

@@ -289,10 +289,10 @@ func (w *worker) _next() {
 		// down the subscriber to free up resources. It'll get started
 		// again if new activity happens.
 		w.Lock()
-		defer w.Unlock()
 		// inside the lock, let's check if the ephemeral consumer saw something new!
 		// If so, we do have new messages after all, they just came at a bad time.
 		if w.ephemeralSeq > w.durableSeq {
+			w.Unlock();
 			w.Act(nil, w._next)
 			return
 		}
@@ -301,6 +301,7 @@ func (w *worker) _next() {
 			logrus.WithError(err).Errorf("Failed to unsubscribe to stream for room %q", w.roomID)
 		}
 		w.subscription = nil
+		w.Unlock()
 		return
 	case nats.ErrConsumerDeleted, nats.ErrConsumerNotFound:
 		w.Lock()