Thank you for being proactive and suppling the Etrecheck report
Your EtreCheckPro report records four Safari crashes but does not establish their cause.
Your Mac’s reported SSD health and available storage look good, so begin by restarting your Mac and testing YouTube in full screen and in a normal window, using the same video and another video.
Temporarily disconnect Tailscale using its menu-bar controls and repeat the tests, then reconnect it and compare the results.
Your report confirms that Tailscale’s Network Extension is running, but this alone does not implicate it.
If the problem occurs only while Tailscale is connected, investigate further before changing its settings or uninstalling it.
You can also review this Tailscale report concerning macOS 27.0.1 and an M5 MacBook Air, although it does not prove the cause of your issue.
If Safari still freezes, temporarily disable Bitwarden under Safari > Settings > Extensions, then test again.
If necessary, re-enable them one at a time.
Next, test YouTube in another browser and in a temporary macOS user account created under System Settings > Users & Groups.
If Safari works in the new account, a user-specific setting or extension may be involved.
Check System Settings > General > Software Update for available updates.
If the problem persists, test in Safe Mode.
Note whether only Safari becomes unresponsive or the entire Mac freezes, and record the time of the next incident so you can locate the corresponding crash report.
If Safari continues to crash, review the report or contact Apple Support.
For further guidance, see Apple’s Safari troubleshooting guide and instructions for setting up Mac user accounts.
EtreCheckPro did not find a Time Machine backup, so back up your Mac before undertaking more extensive troubleshooting.
These tests can help narrow down the cause, but none alone confirms which component is responsible.
