Bug: Call duration timer starts with negative values before counting up normally

When joining a Nextcloud Talk call, the call duration timer initially starts with negative values (for example -1:-1:-33) before it begins counting upwards normally.

The issue is reproducible and occurs for all participants in the call, not just a single client.

The negative values disappear after a short time, and the timer continues counting up correctly. The call itself is not affected (audio, video and screen sharing work normally).

Steps to reproduce

1. Start a new Nextcloud Talk call.
2. Join the call with one or more participants.
3. Observe the call duration displayed in the top bar.

Expected behavior

The call duration should start at 00:00:00 (or 00:00) and count upwards immediately.

Actual behavior

The timer starts with negative values such as:

-1:-1:-33

After a few seconds it automatically switches to a normal increasing timer.

Environment

• Nextcloud Hub 26 (34.0.1)
• Talk 24.0.2
• High Performance Backend (HPB) configured and working
• Docker deployment
• Reverse proxy: Nginx Proxy Manager
• Cloudflare Tunnel
• Ubuntu Server 24.04 LTS

Additional information

• The issue is visible for every participant in the call.
• The timer eventually corrects itself without any user interaction.
• Audio, video, screen sharing and messaging work correctly.
• Server time is synchronized correctly.
• No related errors are visible in the browser console or server logs.

Reproduce the issue by joining a Nextcloud Talk call and observing the duration in the top bar. Trace the frontend call-duration timer and its initial time value; done means every participant sees 00:00:00 or 00:00 immediately, with no negative values, while the timer continues counting normally.