Damper problem

[DJ's Dad]

I'm looking for some thoughts on a problem we've got.

We changed the front springs my my sons B4 from blue to black to see how this impacted the cornering performance. With the black on the "square" white plate in the bottom of the damper has now come adrift twice ending up with the oil leaking from the damper.

We'd been doing counter clock wise circuits on a flat carpet surface to learn about the the spring effects - and interestingly it's only one side (nearside) i.e. inside of the cornering which popped it's square retaining plate.

The first time I thought it may have been a build error but when we re-assembled it it went back together ok with a "click". I've put it back for the third time.

Is there something with the softer springs which make a difference?