Is it only with multiple choice? Seems I cannot create any question type if I switch to pgsql 10.12

It is not with multiple choice. See another bug report: 16563

I have the same problem with for both multiple choice & array questions.

sub-questions are not being saved and a red empty box appears when trying to save (a screenshot is attached)

My configuration: (LS version 4.3.5+200721 - PHP 7.2.1 - Database: MS SQL Server 2016)

Random characters sometimes could come on qid when creating new questions as those are used by vue to identify internally new rows.

Before issue 16469, QuestionEditorController tried to find the questions using 'findByPk', which automatically casts the value to int, removing characters.

Now, 'find' is used because the survey ID is added to the search criterias.
qid is not casted and no objects are found.

When saving a new question, Question object is empty, and the resulting SQL fails in Postgres because of the data type.
Solved by casting 'qid' to int.

PR: https://github.com/LimeSurvey/LimeSurvey/pull/1543
Contains both fix for 16566 and 16563

Tested the issue before pulling the PR, Issue exist. Tested the issue after pulling the PR, below are my findings:
Screenshot 1:Before PR, the question is not been created and a red top bar is displayed
Screenshot 2:After PR, the question is been created and saved successfully and is displayed

Please refer the attachment for more details, working as expected

Fix committed to master branch: http://bugs.limesurvey.org/plugin.php?page=Source/view&id=30372

Fixed in Release 4.3.11+200817