Recurring tasks not compatible with jtxBoard

Steps to reproduce

1. Create a daily recurring task in Nextcloud Tasks
2. Mark it as done in jtxBoard
3. See it is still not marked done in Nextcloud Tasks

Switching what is done in which app leads to the same result.

Expected behavior

The task should also be marked as done in jtxBoard.

Actual behaviour

The task is not marked as done in jtxBoard.

Tasks app version

0.18.1

CalDAV-clients used

DAVx5, jtxBoard

Browser

No response

Client operating system

No response

Server operating system

No response

Web server

None

Database engine version

None

PHP engine version

None

Nextcloud version

34.0.1

Updated from an older installed version or fresh install

Updated from an older version

List of activated apps

Nextcloud configuration

Web server error log

Log file

Browser log

Additional info

I filed the same issue in jtxBoard, because I'm not sure which one is broken and needs fixing: https://github.com/TechbeeAT/jtxBoard/issues/2345

Start by reproducing completion of a daily recurring task in both Nextcloud Tasks and jtxBoard, then compare the behavior with the linked jtxBoard issue #2345. Trace the CalDAV synchronization path used by the Tasks app and determine which side fails to propagate completion; done means marking the task complete in either app also marks it complete in the other.