About 6 months ago, my freezer coils iced up, the drain iced up and I had frozen water in the bottom of the freezer. With help from this forum and other places I managed to run diags on the jazz control board (okay), disassembled the freezer to expose the coils and defrosted them, cleared drain, got it all back to together and has been working since then.
Just yesterday I noticed it had iced up again, fridge was up to 54°, freezer still okay about 0, no water/ice in bottom of freezer. I did a force defrost and was planning to de-ice today. Also saw the new P-tube drain kit (W10619951) to address drain problems on these units and was going to install one of those.
This morning, the fridge was back down to 41° so the defrost opened up the air way enough to get it cooling again. I did another forced defrost and used a heat gun (on low, carefully, slowly… 
to melt ice around the vent slots (did not disassemble freezer to remove back panel). I noticed that the water was draining okay. So my question is - if the drain is not clogged, what is the next most likely problem causing the icing? Maybe I should just do a forced defrost every month or two to help it stay deiced…
Thanks!
Toby