I used to have similar Problems with my old SB PCI (and other Soundboards).

Such problems are independent from GFX installed/used (at least in my case).

It always happened, when too many Sound Channels were used (to each several effects are normally processed and added).

A good number for a SB PCI is something around 16 Channels or less. I found, that using more Channels (24 or even 32), those SFX Problems quickly became severe.

I'd recommend trying reducing the No. of Sound Channels to a lower Value for troubleshooting.
Having the very latest Sound Drivers is mandatory, of course, and significant IRQ Problems have to be resolved first, if present.

Yes, this (usually) can be done from the Game's own Advanced Menu.

If that option is not available, look for a .ini or .cfg File, where all Preferences are stored. Usually, this config File will also contain advanced Sound preferences...