Raygunpanda, You posted your question about your holonomic drive into the EasyC Technical Support Q&A section of the forum. This is an official section so only EasyC representatives can answer your questions there (which I am not). Therefore, any answer you get on there will take longer.
As far as your problem goes, it sounds like one set (either the 293’s or 393’s) of motors on the left side got switched; the front motor was crossed with the rear motor. This would cause the problem you have stated.
To resolve this:
Unplug the 293’s on the left side and test your robot.
If it strafes properly, then plug the 293’s back in, but cross the front and rear motors (e.g if the front was plugged into port 1 and the back into port 2, then now switch them so the front is in port 2 and the back in port 1).
If it does not strafe correctly, plug the 293’s back into the same ports they came from and unplug the 393’s. Repeat the same procedure above. If it still isn’t working with the 393’s unplugged then plug them back in as they were originally and let me know. Hopefully that helps.