Ac motor resets arduino, but arduino stucks there.

I try to control(just on-off) 220v 300w small ac motor with arduino and 2 ways relay module (classic relay module on market, %99 Chinese product). I have 5v 3.2a power supply for arduino nano and relay module. As you know, relay module has flywheel diode, transistor and optocoupler on it. There is a rc snubber + varistor at the output of the relay on the contacts(common - NO, I don't use NC). Ac motor is at least 1 meter away from arduino. Ac cables are approximately 10cm away. I made star grounding with relay grounding and arduino. Relay module get its power from power supply. I added ferrit core on NO cable(5 turns). As you guess, my problem is, after a few times of motor start-stop, arduino resets itself and stuck there. To use arduino again I need to re-upload same code again or else reset button doesn't make difference without uploading the code. The code is very same to standard arduino blink example just mine has 1min delay. What should I do now? Thanks in advance.

You've got to remove the interference that's crashing the Arduino - are you using the relay module in
fully optoisolated mode?

I'm surprised that you need to reload the code. Doesn't cycling the power reset the board?

Yes I use the relay module in fully optoisolated mode.
Disconnecting from power supply or pressing reset doesn't change anything.

Does the Arduino chip get extremely hot?

If so the interfence spike has sent the chip into CMOS latch-up, which can fry the chip.

You have some very severe interference if this is the case, perhaps via the power supply?

I chose a nice quality power supply but it is electronic, anything can possible. I never witnessed mcu getting hot or I didn't notice it. Generally my little on-off works for several days. After third or fourth day, something is going wrong.