R407c Chiller

I've got a client with a chiller rated at 340kw running on 407 which has suddenly seized with no prior indication. The compressor is a Hartford hermetic vertical screw, part winding start with 2 unloaders. From what I can gather from the supplier this type of compressor has been experiencing regular failures due to a manufacturing problem or even a design problem.

Has anyone else come across these compressors?

As they are American manufacture maybe our friends across the pond can shed some light on this?