Investigate why we have so many dysfunctional WebTunnel bridges

According to bridgestrap, ~100 webtunnel bridges are currently dysfunctional, a significantly higher count than obfs4 bridges.

We should investigate these bridges, identify the issues, inform the operators, and evaluate whether the documentation needs improvement.

Tasks

• Investigate and identify the issues
• Inform the operators about the issue and help them to fix it
• Assess potential fixes (e.g., improving bridge operators docs)

(cc @meskio)