The LM324 requires a coulpe of tricks to make it work well. One of them
requires that you ensure that none of the inputs ever go over 3.5V or so
because the output will become +Voutmax immediately. If it is used with a
circuit that allows any of the inputs to become more positive than this
Voutmax then this can cause it to latch up.

There are a number of fixes that remove this problem but you need to work
them out yourself for your circuit.

hope this helps,

Peter

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