Maintaining the board at a at a high temperature for a time tends to vaporize any deposits which could be causing a conduction path, especially in any high impedance part of of the circuit. As you have already cleaned the circuit with IPA- which you had not stated- I don't hold out much hope though. deposits often get under components wher you can'tr see them
The most likely components to go leaky are electrolytic capacitors, especially aluminum types.
You may be able to check a zener diode, if that is what it is, in circuit but without seeing the schematic that would be difficult to say.
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