heisenbug with ansible [core 2.11.2]

gistfile1.txt

$ git diff -c -U4 roles/apache2/tasks/main.yml
diff --git a/roles/apache2/tasks/main.yml b/roles/apache2/tasks/main.yml
index 0be2859..52b6c8f 100644
--- a/roles/apache2/tasks/main.yml
+++ b/roles/apache2/tasks/main.yml
@@ -43,8 +43,11 @@
 - import_tasks: configure_apache2_deb10.yml
   when: ansible_os_family == 'Debian'
     and ansible_distribution_major_version == '10'

+- debug:
+    msg: "{{ ansible_os_family }}, {{ ansible_distribution_major_version }} "
+
 ## centos config (generic)
 - import_tasks: configure_apache2_centos8.yml
   when: ansible_os_family == 'RedHat'
     and ansible_distribution_major_version == '8'