Professor refuses to fix grading criteria (sent out something different to students VS TA's)

My issues is I was deducted thirty points on a project for being late. The project was due Oct 18. That was a long weekend with mon and tue off. He sent out an announcement that the project could be turned it late for Wed the 23 -10 points, Thur the 24 -20 points, Fri the 25-30 points, Mon the 28-40 points and Tue the 29 -50. Latest submission was the 29th

He gave the TA’s grading Oct 19-22 -10 points, 22nd -20, 23rd -30…etc with that last day for submission on the 26th.

Several students are affected. We have all told him and the TA’s the issue. We all have screenshots of his announcement. He promised in class he would fix the issue. He then emailed the TA’s with same criteria he gave them before which is different then what he gave us.

They are all refusing to fix the grades.

What can I do about this?

Have you gone back to the professor a second time? Perhaps explain the original mistake was inadvertently repeated? That’s where I would start.

I suppose if that didn’t work, the group could escalate it to the department chair. That seems a little drastic for what might just be an honest mistake.