KV operations in queue consumers fail often with "503 Service Temporarily Unavailable"

We are experimenting with queues (Beta) and when we run KV operations inside queues they often fail with the following errors without any clear reason:
KV GET failed: 503 Service Temporarily Unavailable
KV PUT failed: 503 Service Temporarily Unavailable

We are deploying with wrangler 2.20.0 and the worker is running with the Unbound Usage Model

Is anyone experiencing the same issue?