volume of some intruments gets lower all of a sudden

changing the volume in any way (mixer, dynamics, etc.) will result in the volume of some random intruments becoming lower (not intentional). Some time this will happen just randomly.
I use some soundfonts that are not from musescore, but i dont know if the problem are said soundfonts or the program itself. A temporary workaround i found is resetting the synthesizer setting and putting all the soundfonts back or closing and reopening the program. This, however, is only temporary cause the problem will come back.