I have not seen where you indicated you replaced the dryer each time the system has been open. The system is VERY sensitive to moisture, more so than commercial A/C systems.
It sounds like you have moisture in the system and it is freezing inside the expansion. Frost is not unusual, ice formation is unusual and one of two things is causing it.
1) Expansion not opening properly due to moisture in the system, or it is faulty
2) Thermostatic sensor not cycling the compressor when the temp get too cold and starts to freeze the evaporator. What pressures did you get after filling the system? Normal is 12-42psi for Low and 150-185psi for High (if ambient is in the 70-82F range).
If both are showing low then the expansion valve is the likely culprit.
Replace the dryer, they suck up ambient humidity in a nano sec. When the dryer in manufactured it is filled with Freon and when you remove the caps it will drift out for about 10 min before air can get back in. The PDF contained in this link will be of help with diagnostics. https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwjPnNaItpj_AhWOOkQIHepKB2MQFnoECBEQAQ&url=https%3A%2F%2Fnissens.com%2FAdmin%2FPublic%2FDownload.aspx%3Ffile%3DFiles%252FFiles%252FAuto%252FPosters%252FNissens_AC_System_Diagnostics_Poster_98x68%2B-%2BOperating%2BPressures%2BR134A%2B-%2BENG.pdf&usg=AOvVaw0qvh-7b6db8k7nt0CyrlN_ Keep us posted.
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17:48:03 05/19/23
