Excess metadata

[muranod]

I have a number of files with a ton of metadata which I am unable to edit and I can't figure out why.  The files are not protected.

In the "Image Description" of the EXIF metadata panel, it shows long strings of characters, like "
U21pdGhzb25pYW4gbXVzZXVtLiBTY2FuIGZyb20gcHJpbnQgLSByZS1lZGl0
IHRoZSBzZXJpZXMgYW5kIHJlc2NhbiBmcm9tIHRoZSBiJncgbmVnYXRpdmVz
LiBOb3Qgc3VyZSBvZiB0aGUgZGF0ZSAtIG1heWJlIDE5OTMuIKkgRGFuIE11
cmFubywgYWxsIHJpZ2h0cyByZXNlcnZlZCBDTEVBTkVE
"

When I click the "I" on the thumbnail, I get different strings of text that look like html, whereas normal files show the IPTC caption and the path of the file. (I can't screen-grab this because it disappears when I touch anything else).

In Photoshop, everything looks normal, and I have tried re-saving the file. The IPTC caption does appear elsewhere in the Imatch metadata panel.

The LOCK icon appears next to many of the metadata panels in Imatch, including the one with the long string above." The files are not protected files.

If I rescan to reeload metadata, I get the message that "Some Metadata is protected   -You have configured option to protect unwritten metadata ... under Edit > Preferences > Metadata."
I can't find any option there to change the behavior I'm seeing.

[Mario]

It seems that the EXIF description in your files contains noise data or the EXIF record does contain an invalid character encoding.
This field is marked as read-only (locked) because it is automatically from the XMP description when you write back. Just write something into the description tag and write-back.
You don't see this kind of issue in PS because PS shows you maybe 10% of the data in your files.