This error indicates that a Kudu tablet server has closed a scanner because it hadn't been accessed in some time. It could manifest on a particularly slow query that very infrequently fetches new data from Kudu.
Can you share the Impala query profile for one of the failed queries, as well as the Impala daemon coordinator log?
You can also work around the issue by reconfiguring Kudu's --scanner_ttl_ms flag to a much higher value (the default is 60s), though this will come at the potential cost of Kudu memory if any clients are orphaning their scanners.