Recurring tasks are displayed in multiple entries after completing one task

[update-freak]

Baikal version: 0.9.5

Current behaviour:
Briefly about my setup in terms of synchronization:
Android: NAS with baikal (docker) <-> DAVx5 <-> aCalender+
Windows PC: Thunderbird via integrated CalDAV function <-> baikal (docker) on the NAS

If I now create a task that repeats every 2 weeks on Friday, for example, and I tick this task off in aCalender+ after completing it,
I have noticed that in Thunderbird the entries for the recurring task appear with different times (see appendix).
I expected that only one entry appears in the task list.
Unfortunately, I don't know exactly where the problem lies (i.e. baikal, Thunderbird, aCalender+).

Expected behaviour:
After tick a recurring to do as completed I expect that I get one one item and not multiple items (see picture).

Steps to reproduce:

1. Create a recurring to do (e.g. every 2 weeks) in e.g. aCalendar+
2. Tick this to do as completed e.g. via aCalendar+
3. Synchronise via DAVx5
4. Check the to do in Thunderbird if there are multiple items