Please make your button definitions, with the field MYFIELD as along as it is unhidden. after this solution works, go to script and use the command line tag field MYFIELD with $hidden. Afterwards the buttons will continue working. 🙂
Rather than a Solution, that is a workaround, in case of a change you need to copy, unhide, reload, edit, hide, reload, publish. A solution would be the one proposed by @rubenmarin that allows flexibility in the form of a calculated result 🙂
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