This issue has been on here for quite a long time now. This issue is found on all electrostars. aka 377s, 387s and 375s. If you try to make a 3 car variant or aka trying to make a /3 variant (expect 387). the connector/gangway rubber would be like this for some reason?. Is there anyhow DTG could fix this problem so we can make /3 variants without any bugs on the formation design?
Same as this: https://forums.dovetailgames.com/threads/class-387-5-car-challenge.80613/ and this: https://forums.dovetailgames.com/threads/br-class-375-gangway-bug.78509/ All electrostars have this issue. Reported in february still not fixed, probably never will be, nothing surprising at all.
