Heat pump is operating under great parameters for outdoor temperature being 26° Unit is heating with a 43° temp rise inside. Unit generating frost outside as intended/expected during cold weather unit can buildup ice chunks and will defrost the ice with normal operation which can take hours at times. Unit is packed full of sensors monitoring its running state and will signal defrost when it knows it’s required. Ice buildup should only be a concern when the blue fins are no longer visible at all around any of the coil sides.