you should deceide whether to use minimized version of jqGrid jquery.jqGrid.min.js downloaded so that it contain all modules which you need of use uncompressed developer version (see documentation). If you include grid.formedit.js or grid.inlinedit.js you have to include dependend module grid.base.js and grid.common.js before.
You try to use form editing without setting editurl parameter of jqGrid. Is the url:'Grid' response also for HTTP POST requests to save the data during the editing?
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