visionOS 27: random dimming, much more heat, and noticeably lower frame rate — anyone else?

Has anyone noticed a significant performance/thermal regression after updating to visionOS 27?

Since updating, my Vision Pro has been behaving very differently from before:

• The displays / Mac Virtual Display randomly become much darker.

• Changing the Brightness slider in Settings seems to do basically nothing when this happens.

• The headset itself gets noticeably hotter than it used to.

• The overall frame rate also feels lower. Head movement and the UI don't feel as consistently smooth as before.

• I'm seeing this even with a pretty light workload — basically just YouTube and Mac Virtual Display.

• I don't use BetterDisplay, Lunar, DisplayBuddy, or any other display-control apps.

Before visionOS 27, I did not have this combination of heat, dimming, and noticeable frame-rate drops.

What makes me wonder about thermal throttling is that Apple documents that Vision Pro can dim the displays when internal temperatures rise, and that visionOS may reduce rendering frame rate under thermal pressure.

I'm curious whether anyone else on visionOS 27 has noticed the same combination:

more heat + random dimming + lower FPS / less smooth performance

Especially interested to hear whether this started specifically after visionOS 27 and whether a restart/full reset made any difference.