Something went wrong. This changeset cannot be further modified.

Good day,

I’ve stumbled upon a problem that I cannot seem to resolve on my own.
So whenever I customize anything under Appearance > Customize it shows just fine in the panel, but when I save the changes and view the page, no customization is saved. Then when I try to access the Customize panel again I’m getting the following error – Something went wrong.
This changeset cannot be further modified.

I’ve tried turning plugins off, changing themes, but without success. Please help!