Based on what you have stated;
1. No AC system leaks.
2. High refrigerant discharge pressure.
3. Vacuum pressure.
In my view, your system has;
1. Excessive ice crystal blockage at the orifice.
2. The blocked orifice is acting like a closed "throttling valve" and increasing the refrigerant discharge pressure.
3. The blocked orifice is also limiting the amount of liquid refrigerant that can "flash to gas" (i.e. phase change of liquid refrigerant to gas refrigerant) in the evaporator.
4. Because less liquid refrigerant is being "flashed to gas", in the evaporator coil, less heat is being extracted from the warm air that is flowing through the evaporator.
5. To remove the ice, the ice must first melt, then vaporize to water vapor and then the water vapor must be extracted by the vacuum. The lower the vacuum, the faster the water vapor can be extracted from the AC system.
6. It takes time to extract ALL the water vapor from the AC system. Sometimes, the water vapor, extracted from the liquid refrigerant, gets trapped in pockets in the AC system and can't be completely vacuum extracted out.
In my view, you need to pull a vacuum of 5000 microns or LESS for a couple of hours or more. Likewise, to remove any trapped pockets of water vapor it is helpful to vacuum the system, run/recharge the AC to redistribute the refrigerant/water vapor, then vacuum again to remove more water vapor, and then recharge with refrigerant. Sometimes I'll repeat this "vacuum/recharging AC" cycling a number of times to thoroughly remove ALL the water vapor. Then if this approach dosn't work, its time to pull the AC system apart.
Best regards,
CJR