Does the two rod ends connect to your solid axle and one link to the car's frame? If so it looks like someone tried to make a 4-link into a 2-link. Lots of torque being applied to tube as it becomes a one tube. It probably wasn't curved when 1st built.
A 4-link looks like this.
https://www.google.com/url?sa=i&url=...AAAAAdAAAAABAK
Of course this is all conjecture on my part and you could have an IRS, etc...