Almost all tasks are created on my phone with OpenTasks.
I installed DAVdroid before OpenTasks, and when there is a new version of OpenTasks or DAVdroid, I remove and re-install both, always in the order in the FAQ. I have one local task list and 6 remote task lists on the same Owncloud account. All task lists are created with the same Android DAVdroid account.
When a create a new task, I start to write a item list. When it take a time to think about all the things to do, it can take two, three or more minutes. And sometime a part of the last items disappeared.
I try to find a way to reproduce it everytime, and I tell you
Thank you so much for your help. That was the issue. Apparently Litespeed v1.5.8 introduced this bug. Updated to 1.5.9 and everything is going swimmingly. You might want to put up a note for any other users who have this issue.