Hi BorodMorod,
When you say ‘converted to 4.8p3’, did you actually choose the ‘convert in place’ option, or did you make a copy of your project for use in the preview? Convert in place sometimes does strange things to project blueprints.
If that was the case, can you try making a copy of your 4.7.6 version project and opening it in the 4.8 preview?