SV06 Plus mid print layer separation

[payne9999]

Printing LW PLA and running 4 SV06 Plus printers in the shop. 3 print fine and one suddenly starts having layer separation mid print. The first part of the print has an excellent first layer and good fusion and the part is very strong. Somewhere along the way it starts to have lamination issues and the part literally falls apart in my hands while the early part of the print is very strong. I am an experienced printer and have seen and solved many problems but this one has me baffled.
Filament: SainSmart LW PLA (foaming)
Temperature: 235C
Bed: 60C
Print Speed: 60mm/sec
Printer setup: In enclosure
Cooling: 40% (recommended by the designer)

Any help would be appreciated,

Nikko