Capturing timer value based on external interrupt , leveraging the 62.5nsec (16MHz) resolution) of the ATMEGA328 on the Arduino Uno

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@johnwasser, @jremington, @johnRob, and anyone else, I need help. I can't figure out what is going on. The Arduino seems to be going through reset at random points. However, when I scope out the RESET pin, it never moves, but I do see the execution of code that should only have happened once. Perhaps memory is getting corrupted somehow?

So, for debug purposes, I've put all the code (except for the timer/capture ISR) in the setup() function:

volatile unsigned long dlyTime;
volatile boolean triggered;

// These constants won't change:
const int COMPIN = 7;    // PD7 used as input to comparator
const int RST_B = 5;    // PD5 used for reseting capacitor
const int comp_int=4;   // PD4



ISR (TIMER1_CAPT_vect)
{
  // grab counter value before it changes any more
  dlyTime = ICR1;  // see datasheet, page 117 (accessing 16-bit registers)
  TCCR1B = 0;// Timer 1 control register 8-bit -- Normal Mode/Clock source stopped
  triggered = true;
  digitalWrite(comp_int,0);
  //TIMSK1 = 0;    // no more interrupts for now
  return;
}  // end of TIMER1_CAPT_vect
  
void setup() {
  pinMode(comp_int,OUTPUT);
  digitalWrite(comp_int,0); //  debug interrupt pin
  
  Serial.begin(9600);       
  Serial.println("Tau");
                                                
  TCCR1A = 0; // Timer 1 control register 8-bit -- Normal Mode
  TCCR1B = (1<<ICNC1)|(1<<ICES1);// Timer 1 control register 8-bit -- Normal Mode/Clock source stopped; falling edge

  //Setup Comparator
  Serial.println("in setup_comp");
  //Set up Comparator
  //reference voltage AIN1, sense on AIN0 (using bandgap ref on AIN0, interrupt on falling edge of COMPOUT)
  ADCSRB = 0;  // disable mux--AIN1 connected to neg input of comparator
  ACSR |=(1<<ACBG)|(1<<ACIC)|(1<<ACIS1); // bandgap selected
  delay(100);
  ACSR &=~(1<<ACD); //enable comparator by clearing ACD bit
  Serial.print("ACSR = 0x");
  Serial.println(ACSR,HEX);
  DIDR1 = (1<<AIN1D)|(1<<AIN0D);
  Serial.println("leaving setup_comp");

  //Reset the capacitor
  Serial.println("in reset_cap");
  pinMode(RST_B,OUTPUT); 
  digitalWrite(RST_B,1);
  delay(200);
  digitalWrite(RST_B,0);  //drive output low to reset sense capacitor
  TCCR1B = 0;
  TCNT1 = 0; //reset counter
  TIFR1 = (1<<ICF1)|(1<<TOV1); // clear flags so we don't get a bogus interrupt
  ACSR  |= (1<<ACI); //clear any comparator interrupt
  triggered = false;

 //Start the timer
 Serial.println("Timer Started...");
   TIMSK1=(1<<ICIE1)|(1<<TOIE1);  //interrupt on Timer 1 input capture and overflow
   //TCCR1B = (1<<CS10);  //timer started
   ACSR |=(1<<ACIE);//enable comparator interrupt
   TCNT1=0;
   Serial.print("TimerCount = 0x");
   Serial.println(TCNT1,HEX);
   TCCR1B |= (1<<CS10);  //timer started
   pinMode(RST_B,INPUT);  // switch port to comparator input
  
  //wait until interrupt
  while(!triggered)
  {
    Serial.print("ACSR = ");
    Serial.println(ACSR,HEX);
  }
  Serial.println("interrupt received, timercnts = 0x");
  Serial.println(ICR1,HEX);

}

void loop() {
  // put your main code here, to run repeatedly:

}

Here's a capture of the Comms console:

2021-10-01_15-39-32
2021-10-01_15-39-32707×448 23.8 KB

All I have connected to the Ardunion UNO is an RC network from 5V to GND, with the common node connected to pins PD7 and PD5 on the Arduino UNO. I'm powered off of USB.

I would appreciate any suggestions!
Thank you.