When you install mixture, you can't edit an legacy cubemap in HDRP

[penguin21]

Only happends when you install mixture.
Screenshot:

Only show if your inspector is in debug mode but is not debug mode

[alelievr]

Hello, the issue is on Unity side and have been reported here: https://issuetracker.unity3d.com/issues/reflection-probe-inspector-preview-breaks-whith-custom-cubemap-inspector
The fix should be released on most version now, which Unity version are you using?