First, I'm an Asian user, so sorry for my poor English vocabulary.
My Photoshop is Windows version 19.1.1 and I think Adobe Photoshop CC 2018/Required/CopyCSSToClipboard.jsx didn't written out from ESTK with UTF-8 signature.
I found codes involved in those error, 'CopyCSSToClipboard.jsx' and 'CopySVGToClipboard.jsx'. In the former code, I found this comment :
// IMPORTANT: This file MUST be written out from ESTK with the option to write the UTF-8
// signature turned ON (Edit > Preferences > Documents > UTF-8 Signature). Otherwise,
// non-English Windows systems.
I'm non-English Windows user, so I found my problem finally. After found it, I installed Extend Script Toolkit and copy the code and save as same file name, covered existing file.
Then, everything were working. Therefore I think CopyCSSToClipboard.jsx didn't written out from ESTK with UTF-8 signature.
I will be waiting for official user's reply. Thanks.
To report a bug to Adobe you would use Photoshop Family Customer Community this is a user forum site. However looking at my system I see that that script file was update March 1 2018. So Adobe may have fixed the problem in the March 19.1.2 update you seem to still be on version 19.1.1.