Creation date changes to Edit Date when image is edited in Photoshop

This now seems to have resolved itself - it did seem to be linked to the fact that Lightroom was being painfully slow in updating metadata 

I can confirm that the problem occurs when lightroom is writing the metadata to the xmp files. I no saving activity is underway then everything behaves normally and the PSD file is stamped with the creation date from the RAW file.

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This problem doesn’t occur on my LR 15.4.1 / PS 27.8.0 / Mac OS 26.4.1 either:

So there’s likely something specific to your installation or the particular files you’re editing.

BTW checked all the preferences in LR and PS and can’t see anything there that could be affecting this.  

The problem may be caused by corrupted preference files, not necessarily a setting you’ve made. LR and PS unfortunately soil their preference files occasionally. So try resetting the preference files as suggested by Johan.

it seems to happen when lightroom is saving metadata

Do you mean that the problem occurs when you have enabled Catalog Settings > Metadata > Automatically Write Changes Into Sidecars?  Or do you mean something else?

If resetting preferences doesn’t help, share one of the problem raw photos along with its catalog metadata:

1. In Library, select the photo.

2. Do File > Export As Catalog, selecting the options Export Select Photos Only and Export Negative Files.

3. Zip up the exported catalog folder and attach it here. If it’s larger than 47 MB, then upload it to Wetransfer, Dropbox, Google Drive or similar free service and post the sharing link here.

I can’t check it right now, but if it just started happening, then most likely this is caused by some corruption. Likely candidates are the Lightroom Classic preferences and the Photoshop preferences. Try resetting them one by one, starting with the Photoshop preferences (because Photoshop writes the file with the wrong date). 
https://helpx.adobe.com/photoshop/desktop/get-started/settings-and-preferences/reset-preferences.html If that doesn’t work, then try Lightroom https://helpx.adobe.com/lightroom-classic/desktop/introduction-to-lightroom-classic/reset-preferences.html

Update: I just did a quick test with Lightroom Classic 15.4.1 and Photoshop 27.8 and I cannot reproduce what you see. When I send a raw file (also Sony) to Photoshop, the resulting TIFF has the correct date.