"doth" system test fails the "testing XoT server functionality (using dig)" check intermittently

The doth system test fails the testing XoT server functionality (using dig) check intermittently:

https://gitlab.isc.org/isc-private/bind9/-/jobs/2440418

In dig.out.ns1.test1, the following error can be seen:

;; communications error to 10.53.0.1#30180: end of file

dig retries the transfer after the above error is encountered and this time it succeeds (I checked the retried transfer's contents using a manual digcomp.pl run).

In ns1/named.run, the following message is logged:

11-Apr-2022 08:14:41.529 client @0x7f4d88d43000 10.53.0.10#46511 (example): transfer of 'example/IN': send: TLS error

There is not a lot to go on from here.

Here is how the transfer process looks like from the server's perspective:

$ grep -F 46511 ns1/named.run 
11-Apr-2022 08:14:41.489 client @0x7f4d88d43000 10.53.0.10#46511: TCP request
11-Apr-2022 08:14:41.489 client @0x7f4d88d43000 10.53.0.10#46511: using view '_default'
11-Apr-2022 08:14:41.489 client @0x7f4d88d43000 10.53.0.10#46511: request is not signed
11-Apr-2022 08:14:41.489 client @0x7f4d88d43000 10.53.0.10#46511: recursion not available
11-Apr-2022 08:14:41.489 client @0x7f4d88d43000 10.53.0.10#46511 (example): AXFR request
11-Apr-2022 08:14:41.489 client @0x7f4d88d43000 10.53.0.10#46511 (example): transfer of 'example/IN': AXFR question section OK
11-Apr-2022 08:14:41.489 client @0x7f4d88d43000 10.53.0.10#46511 (example): transfer of 'example/IN': AXFR authority section OK
11-Apr-2022 08:14:41.489 client @0x7f4d88d43000 10.53.0.10#46511 (example): zone transfer 'example/AXFR/IN' approved
11-Apr-2022 08:14:41.489 client @0x7f4d88d43000 10.53.0.10#46511 (example): transfer of 'example/IN': AXFR started (serial 1397051952)
11-Apr-2022 08:14:41.489 client @0x7f4d88d43000 10.53.0.10#46511 (example): transfer of 'example/IN': starting maxtime timer 7200000 ms
11-Apr-2022 08:14:41.497 client @0x7f4d88d43000 10.53.0.10#46511 (example): transfer of 'example/IN': sending TCP message of 10235 bytes
11-Apr-2022 08:14:41.501 client @0x7f4d88d43000 10.53.0.10#46511 (example): transfer of 'example/IN': sending TCP message of 9988 bytes
11-Apr-2022 08:14:41.513 client @0x7f4d88d43000 10.53.0.10#46511 (example): transfer of 'example/IN': sending TCP message of 9988 bytes
11-Apr-2022 08:14:41.525 client @0x7f4d88d43000 10.53.0.10#46511 (example): transfer of 'example/IN': sending TCP message of 9988 bytes
11-Apr-2022 08:14:41.529 client @0x7f4d88d43000 10.53.0.10#46511 (example): transfer of 'example/IN': send: TLS error
11-Apr-2022 08:14:41.529 client @0x7f4d88d43000 10.53.0.10#46511 (example): request failed: operation canceled
11-Apr-2022 08:14:41.529 client @0x7f4d88d43000 10.53.0.10#46511 (example): reset client
11-Apr-2022 08:14:41.529 client @0x7f4d88d43000 10.53.0.10#46511: freeing client

This does not look like a timeout to me.