Program gets stuck in for loop after interrupt runs

This has me scratching my head - my program runs fine UNLESS the interrupt occurs, after which it gets stuck in a for loop near the start of the program. I can't see any way these two things are connected with each other - there dont share variables. The main loop is as follows

int main(void)
{
 HAL_Init();
 SystemClock_Config();
 
 MX_GPIO_Init();
 MX_ADC1_Init();
 MX_SPI1_Init();
 MX_TIM1_Init();
 MX_TIM2_Init();
 MX_TIM16_Init();
 
 ADC12_COMMON ->CCR |= 1<<19 | 1 <<17; // set ADC clock options
 ADC1->CR |= 1>>0; // enable ADC
 ADC1->CR |= ADC_CR_ADSTART; // start conversion
 
 HAL_TIM_PWM_Start(&htim1, TIM_CHANNEL_1);
 HAL_TIM_PWM_Start(&htim1, TIM_CHANNEL_2);
 HAL_TIM_PWM_Start(&htim1, TIM_CHANNEL_3);
 
 HAL_TIM_PWM_Start(&htim2, TIM_CHANNEL_2);
 HAL_TIM_PWM_Start(&htim2, TIM_CHANNEL_4);
 
 HAL_TIM_PWM_Start(&htim16, TIM_CHANNEL_1);
 
 while (1)
 {
	 while(((ADC1->ISR) & 0b00000100)==0)
	 {
	 }
 
 		for(j=0;j<10;j++)
		{
		 ADC_result_pre[i][j] = ADC1->DR; //fetch adc data
		}
		VCA_raw[i]= (ADC_result_pre[i][0]+ADC_result_pre[i][1]+ADC_result_pre[i][2]+ADC_result_pre[i][3]+ADC_result_pre[i][4]+ADC_result_pre[i][5]+ADC_result_pre[i][6]+ADC_result_pre[i][7]);
		ADC_result[i] = VCA_raw[i] / 8;
 
 
		switch(ADC1->SQR1) //switch dac channel to the next
		{
		case 0b101000000:
		 ADC1 ->SQR1 = 0b110000000;
		 i=1;
		 break;
 
		case 0b110000000:
		 ADC1 ->SQR1 = 0b101000000;
		 i=0;
		 break;
		}
 
		ADC1->CR |= ADC_CR_ADSTART;
 
//======================================================================
 
		LED1_prep = ADC_result[0]>>4;
		RED1 = 255 - LED1_prep;
		BLUE1 = LED1_prep;
 
		if(RED1 <= 127)
		{
			GREEN1 = RED1*2;
		}
		else
			GREEN1 = BLUE1*2;
 
		set_rgb1(RED1,BLUE1,GREEN1); //second spot is actually blue // third is green
 
		LED2_prep = ADC_result[1]>>4;
		RED2 = 255 - LED2_prep;
		BLUE2 = LED2_prep;
		if(RED2 <= 127)
				{
					GREEN2 = RED2*2;
				}
				else
					GREEN2 = BLUE2*2;
 
		set_rgb2(RED2,BLUE2,GREEN2); //1st green, 2nd red, third blue
 
//========================================================================
 
		Prepare_States(ADC_result[0],0); //get the mode info for the first channel
		prep_values(0);
 
//		dac_channel = 1;
		Prepare_States(ADC_result[1],1); //and for the second
//		prep_values(1);
 
 }
}

It gets stuck on the for loop on line 32. I can see j incrementing up to 9, then it gets reset and stays in the loop. The interrupt is as follows

void EXTI15_10_IRQHandler(void)
{
		uint32_t mask = 0;
		uint32_t Chuff = ChangeFlag;
 
		if (Chuff & 1<<2)
			mask = (1<<4);
		else
			mask = (1<<20);
 
		if (Chuff & 1<<3)
			mask |= (1<<12);
		else
			mask |= (1<<28);
 
		GPIOA->BSRR = mask;
 
		Chuff |= 1<<0;
		ChangeFlag |= Chuff;
		EXTI->PR1 |= 1<<11; //turn off interrupt request
}

I can't see any way these things are related. Any help much appreciated!