STM32:496 ADC1/2 dual mode, ADC3 independent?

[BSmit.2]

I am using STM32L496 with ADC1/ADC2 in dual regular simultaneous mode with DMA and seeking to have ADC3 independent sinple single conversion. Code works either with ADC1/ADC2 or ADC3 but not with both. Can ADC3 run independent if ADC1/ADC2 are dual?

[waclawek.jan]

And what does the RM say?

JW