Synthio has one (and likely more) spots where it is possible to overflow the int32_t used as an intermediary while doing fixed point math.

This function multiplies an int32_t by int16_t which can exceed the 32 bit size.

There are likely other cases as well.

The probable fix is to add a function to ensure the values are saturated after every calculation.
audiofreeverb does this

This issue is most likely the cause for #10200.