1. I used instructions from http://www.fossil-scm.org/fossil/doc/tip/www/custom_ticket.wiki to add the assigned_to and opened_by fields to the ticket system.

2. Created new ticket. There is no access to assigned_to field so it defaults to 'unassigned'.

3. Edited this ticket. Changed the assigned_to field to another of the pulldown list values, AND appended a remark in the description and comment field.

4. Clicked on 'Submit Changes'.

5. Result was re-display of view ticket page with neither change made.

6. Edited this ticket again. Changed the assigned_to field again.

7. Clicked on 'Submit Changes'.

8. Result was re-display of view ticket page with the new value of the assigned_to field as expected.

9. Created another new ticket and edited to append text only. This change was accepted with assigned_to remaining as 'unassigned'.

10. Made second edit of ticked to change assigned_to and it was accepted.

It appears that the combination of edits to the two fields cause a failure where single field changes do not.

I did not try other field combinations.

Edit ticket fails to save changes if assigned_to AND remark are changed.