If you get this error with the message: skip must be made from valid record number; this means you've tried to do a FINDV N or P, or you are in a SCAN command and, for some reason, you have cleared the record buffer or at least the record number. This would generally happen during a SAVE command. In this case add the NOCLR option to the SAVE command and your loop should work just fine.
You can also check for an active record before you do the next or previous by using the IFNA() function. If it returns True then you know the next or previous will just return an error and you can protect it before the FINDV command. In the case of a SCAN, make sure you don't clear the record number or buffer of the file you are scanning.
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