Airpods 4 ANC firmware update glitch

Hi, after updating my iPhone to iOS 26, my AirPods 4 ANC attempted a firmware update. Since then, they no longer function correctly as a pair.

• When I opened the case for the first time after the "update", my iPhone showed that the two AirPods cannot connect properly and suggests deleting and reconnecting them.
• Reconnection attempts failed: the case continues flashing orange, and resetting the AirPods and case did not help.
• If I put only one AirPod in the case, I can connect each earbud separately, but not together.
• After a while figured it out, that the current firmware versions (only the right got a successful update):
  • Right AirPod: 8A356
  • Left AirPod: 7E93
• Because of the mismatch, the two earbuds cannot work together. I have already tried the recommended steps: leaving the case and AirPods charging overnight, with the iPhone charging and on Wi-Fi nearby. However, the left AirPod still refuses to update.

At an Apple service center, I was told the firmware should update automatically if kept charging, but this has not happened. Could the firmware mismatch prevent the update permanently, and does this mean the left (or right) AirPod needs to be replaced? Do you have such experience?

Thank you for your help.