Confirmed by the bug reporter that it's indeed an issue on their end. Closing this bug report as it's not a site related bug.
It seems like a bug similar to this one. No one has reported a similar issue so far, and I believe there's something on your end indeed (a software or something conflicting with the site). Did you try testing with another browser and another device (PC, phone, etc.)? Are you having the same issue even on another device?
For any replies, feel free to send me PMs, or just update this bug itself with a highlight of the new reply/update.
Hi there. I'm able to use any button just fine (not tested the ones in the Edit form, though). Perhaps, it's an issue on your end. Do you have any browser plugins/extensions installed? Try a hard refresh of the page and see if it works.