NX 12 - Drafting: Slow when switching between sheets

Hi. I want to know if somebody face the same problem with me but already found the solution.

Situation:

- I have .prt file with modeling and drafting inside, 117 drawing sheets. 290mb file size. Done in NX 10

- File stored in server

- In NX 10 there is no long delay switching between sheets (normal 1-2 sec)

- My PC is Xeon E3-1220 with Nvidia Quadro M2000

Problem:

- Now the file is edited in NX 12. There is long delay switching between sheets (around 20 seconds)

I tried the 'part cleanup', the 'update external changes' and the 'feature playback'. But no luck, please help.

Thanks