Sudden drop of volume in Groove Agent or other VST plugins

Hi everyone, i have some issue with cubase. Since a couple of days there is a sudden drop in volume when i´m working with Groove Agent SE4, the same issue with some external vst Instruments. I checked all automations, levelers everything is normal, but there is this sudden drop of volume. Had someone the same problem and a solution? Thanks.

Cubase Elements 9 Version 9.0.30 Build 266 (64bit)
PC Configurations:
AMD FX ™ - 6300 six core 3.50Ghz 64bit
16GB rams
3TB HDD and 110gb SSD
Graphic Card Gigabyte AMD Radeon ™ R9 200 Series 2GB
Windows 10 Home