Items put on Queue in thread in child process sometimes not seen by parent process

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2020-08-22.11:42:15.115>
labels = ['3.7', '3.8', '3.10']
title = 'Items put on Queue in thread in child process sometimes not seen by parent process'
updated_at = <Date 2020-08-22.11:42:15.115>
user = 'https://github.com/alexmojaki'

bugs.python.org fields:

activity = <Date 2020-08-22.11:42:15.115>
actor = 'alexmojaki'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = []
creation = <Date 2020-08-22.11:42:15.115>
creator = 'alexmojaki'
dependencies = []
files = ['49422']
hgrepos = []
issue_num = 41614
keywords = []
message_count = 1.0
messages = ['375795']
nosy_count = 1.0
nosy_names = ['alexmojaki']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = None
url = 'https://bugs.python.org/issue41614'
versions = ['Python 3.6', 'Python 3.7', 'Python 3.8', 'Python 3.10']