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I've had problems of the same sort. I think it comes down to a design problem: awaiting an inner callback inside of an outer callback invites the problem of deadlocks. The way to solve it, I believe, is through callback groups.

Have a look at these links for more information: https://docs.ros.org/en/foxy/How-To-Guides/Sync-Vs-Async.html#asynchronous-calls

https://github.com/ros2/examples/blob/foxy/rclpy/services/minimal_client/examples_rclpy_minimal_client/client_async_callback.py