4 Door RLN-4 Frozen Food Case Froze Up

YT199 Arrived onsite and checked in with manager. Told me that the Aisle for cases A14 was causing problems again, and doesn't know why this keeps happening. He took me to the E2. I checked and found that the A14_3 Case was the problematic area today. Went back to case and found no Airflow at top. I got a cart and removed the bottom shelves product and took to the Walk In Freezer. Removed the Bottom Covers for access to the evaporator, and found the Evaporator Frozen up and completely blocking airflow across. This store uses a overhead vacuum drain, and cannot be washed with hot water through hose. Went back to E2 and forced a Manual Defrost to defrost and test defrost cycle. Hot Gas Defrost appears to be operating normally with no issues. The fan cycles off and the fan temperature switch reaches proper temperature. Cycles are only 25 mins in duration 1 time per 24 hrs. I had to force 4 Defrost cycles to clear out all the Ice from the A14_3 Evaporator. Once this was done, airflow still was blocked by a wall of Ice 2-3" thick against the outlet side of the evap. Had to haul hot water in large trash can and Pump Spray it into the back bottom corner of the 4 door case all the way across to melt the this slab of ice blocking air. Once I finally got all of this Ice melted, air flow was restored. Clean up mess, restart the case and observed E2 temperatures. During this call I also was on the roof at Rack A and recycled power to the EEPR Board for Case A07, which resolved the issue of freezing the product, for which we have a separate ticket for. I will close that ticket out with no time on it. At this time, a direct cause for the the A14 case to freeze up the way it did Cannot be 100% confirmed. The Defrost Cycle is operating normally and all sequences of operation are normal. The previous call that the manager referred to I found to be on January 29th and involved the A14_2 5 Door Case, Which is not the case I worked on today. It is possible that the 25 minute defrost cycle once per day cannot remove all the moisture that is introduced into these cases, especially and particularly if the cases are left wide open when they are being stocked overnight. I recommend that the stockers try to keep the doors closed whenever it is not specifically being stocked. Leaving multiple doors left wide open and walking away from them, leaving them unattended- if that is occurring-will cause this issue. Both jobs received today Completed on this ticket.