Flutter Flow - Custom Action Not working on Android APK

Answer ( For future, if anyone encounters same problem )

It appears that the issue causing the error was in the following line of code:

String shelfGuageMap = '{"14": 2, "16": 1.5, "20": 1}';
String angleGuageMap = '{"14": 175, "16": 150, "18": 130}';
Map<String, dynamic> shelfGuages = json.decode(shelfGuageMap);
Map<String, dynamic> angleGuages = json.decode(angleGuageMap);

It seems that Flutter Flow does not support String to Map conversion on Android or at least not in this specific case. To resolve this issue, the whole logic was changed to:

String shelfGuageList = '["11:3", "12:2.5", "13:2.5", "14:2"]';
String angleGuageList = '["11:140", "12:150", "13:160", "14:175"]';
List<String> shelfGuageToList = json.decode(shelfGuageList).cast<String>();
List<String> angleGuageToList = json.decode(angleGuageList).cast<String>();

After making this change, the code started working on all devices.