Voltage Drop from 3.3V to 1V on NRST Pin of STM32F070CBT6

[parvej alam]

I am using STM32F070CBT6. I am experiencing voltage drop on NRST Pin from 3.3V to 2V or 1V randomly for few milliseconds then it goes high to 3.3V. This drop comes randomly in every 2 to 3 minutes. My VDD is stable I checked the same on Oscilloscope.

Below is schematic and oscilloscope screenshot.

[parvej alam]

Can you please any solution. Its very important to me. Pins are correctly tied up as per MCU pinout description in datasheet (I have double cross checked the same). Even their is no power (VDD-3.3V) fluctuation. VDD is smooth. This problem remains even if i download simple LED blinking program or erase the entire chip.

[parvej alam]

In fact if anyone help me out from this. I am ready to pay for the solution.

[MikeDB]

Have you monitored the GND at the VSS pins against the GND on the power supply ? That sounds like the whole power rails are collapsing which would indicate a too heavy load (short?) somewhere. Post some photos of your PCB both sides