You should only gel an ink when you flash it. 180 degrees. If you cure the underbase, the top color will not stick to it.
My usual question: How are you measuring?
If you answer that you
aren't, you have the problem.
To measure temperature you need a contact thermometer for the best accuracy or an infra-red thermometer for pretty good accuracy.
Here is a good variety of thermocouple thermometers from Cooper Instruments with prices from one of their distributors. Look for the Screen Printers ThermoProbe kit. This used to be called the Atkins ThermoProbe until Cooper bought Atkins.
manufactured by Cooper-Atkins
You want a K Type probe. I like the model 50319-K:
Food Safety Temperature Monitoring Wireless HACCP
IR Thermometers are not as accurate as a contact thermometer.
Grainger Industrial Supply