Android App: Manage (periodic) todos/tasks with CalDAV

Question

Current Setup

I want to manage calendar entries and tasks on a windows and an android device. Currently I use:

• data hosting: fruux.com (access through CalDAV)
• on windows: thunderbird + lightning plugin
• on android: fruux app (for sync) and aCalendar Pro (for viewing)

What's (not) working

On the PC side everything works fine and as expected; on Android I can see the tasks in the fruux app, but can not edit them nor tick them off.

Apps I've tried

• DAVdroid: syncs the data including the tasks, which works!
• aCalendar Pro: once synced with DAVdroid it can assess all tasks, but when I try to check off a periodic task, all repeating tasks are checked off.
• OpenTasks: Same issue as aCalendar
• Buisiness Calendar 2: Doesn't recognize CalDAV task list
• 2Do: only IOS/MAC version supports CalDAV

Question

Can anyone recommend me an App that can handle periodic tasks?

I do like CalDAV because it does not tie me to a specific app / service, has no recurring fees and I can use fruux which does have decent data encryption. If you know a todo-app that does not use CalDAV, but has these properties I'd like to hear about it as well.

Footnote

I think the problem lies with the front-end app on android, but I'm not 100% sure. That's why I've included my whole setup.

Answer 1

Update 2020: The combination DAVx5 (DAVdroid successor) + OpenTasks now works with periodic tasks, no workaround is necessary.

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Although I did not find a suitable app, I did figure out an acceptable workaround (for me):

1. Create a new calendar on fruux.com (or whatever service you use) for periodic tasks
2. Add the service to DAVdroid
3. Tap on the three dots and tick the "force write protection" box
4. Use OpenTasks or aCalendar Pro to view the task and get the notification
5. Tick of using Thunderbird once you have access to a PC

This setup prevents accidentally deleting future periodic tasks by checking off the current one. This is especially useful for infrequent tasks such as paying a yearly membership fee.