How I made a radio transmitter on the CD74HC14 chip but something is wrong here

Today I decided to test a radio transmitter for a frequency of 3.57 MHz, which I made on the SN74HC14N microcircuit. This microcircuit contains six inverting Schmitt triggers. I assembled it according to the scheme shown in the photo. The master oscillator is made on one trigger and a quartz resonator for a frequency of 3.57 MHz. Next comes the buffer cascade and a power amplifier on four triggers. Instead of an antenna, I connected a 50 Ohm resistor to the load. With a power supply of 5 volts and a current consumption of 20 mA, the output power was 67 mW. And everything would be fine if I did not switch the oscilloscope probe divider to ten.

Now the oscilloscope shows a triple transmitter frequency of about 10.7 MHz. This bothered me a bit and I spent the whole evening trying to figure it out, but in the end I realized that it is better not to make a transmitter on this microcircuit, after all it is a logical microcircuit.

But I have another similar microcircuit, only MM74C14N, it is also a Schmitt trigger, but with a power supply from 3 to 15 Volts. In this radio transmitter circuit, this microcircuit starts working from about 9 Volts, it will not work below. But if you switch the divider to 10 on the oscilloscope probe, the frequency will remain stable at 3.57 MHz, and not multiply by three.

On the left in the photo, the microcircuits operate at 9 volts, and on the right at 5 volts of power supply.

The operation of the microcircuits was tested only in this circuit, in other devices that are not for high frequencies, these microcircuits will work according to the datasheet