When a draft message subject contains a non-utf8 character, the draft can be saved, but if it is reloaded and re-saved, it triggers an sql error like:

1/1) ContextErrorException

User Error: SQL ERROR [ mysqli ]<br /><br />Incorrect string value: '\xF0\x9F\x86\x9A H...' for column `sql_explain`.`phpbb_drafts`.`draft_subject` at row 1 [1366]<br /><br />SQL<br /><br />UPDATE phpbb_drafts
SET draft_subject = 'Re: C8 [non-utf character here] Heatwave, Heatwave winning/won...', draft_message = '<r><QUOTE author=\"mike\" post_id=\"3\" time=\"1786639756\" user_id=\"2\"><s>[quote=mike post_id=3 time=1786639756 user_id=2]</s>test post<e>[/quote]</e></QUOTE></r>'
WHERE draft_id = 2
AND user_id = 2
in driver.php line 1031
at driver->sql_error()in mysqli.php line 216
at mysqli->sql_query()in factory.php line 353
at factory->sql_query()in ucp_main.php line 630
at ucp_main->main()in functions_module.php line 684
at p_master->load_active()in ucp.php line 383

I will submit a patch.