I think it's a perfectly valid word TBH -admittedly not an everyday work unless you read Japanese comic books perhaps. If I'm struggling the two strategies that come to mind are 1) it's a double letter - possibly involving one of the letters that is already identified as correct, and 2) it's an American spelling - we had one recently but can't recall - it was something like ARDOR (not ARDOUR) - or ARBOR/ARBOUR, LABOR/LABOUR, etc. I lost my streak of 55 simply by forgetting to do it one day 😪