I'm not 100% certain this is the issue you're having, but I'd guess 2 things are going on here. You're probably in "Auto" on the thermostat, with the fan set to be constant-on rather than auto. It doesn't seem like it should do what you're describing at those temps, but it's my first guess.
Make sure the thermostat is set to "FURN" rather than "AUTO" (and check your fan settings) and see if that improves its behavior.
Zero Gravitas ó 2017 Flying Cloud 26U | WBCCI# 15566
He has all of the virtues I dislike and none of the vices I admire. ó Sir Winston Churchill