I am working on a ruud heat pump MN# upne-048jaz with an electric air handler inside mn#uhla-hm48 with R-22 coil mn#rcsa-hm4824au. The home owner called with a complaint of freezing up on hot days with 85 degrees and up. Unit is 4 years old and this is the first hot summer we have had since it's install (not an install of mine). With 80 degree ambient outdoor it has 180# head, 50# suction with 50 degree line temp. We sucked it down and purged with nitrogen and vacuum and weighed in a new charge. Checked the pressure drop across filter drier and all seems to be well there. Replaced txv and no change with that either. Have cycled unit into heat mode in hopes that if there was oil in distributor tubes when in heat mode i do have a slight pressure difference from each port. Any ideas?