Sefaria has a very nice feedback mechanism. If you see some issue on their site, you can report it. On the sidebar, it is under Tools / Feedback.
You can choose the type of feedback, and I selected Report a Bug:
I directed them to the Vilna page for Zevachim 42a (which they have listed under manuscripts) and pointed out their bug:
Zooming in, the bug is in Tosafot, dibbur hamatchil kegon:
Elementally foundationally truthfully & definitionally you found the bug💯