What is Amortization re-cast period?

Answer: Pre-determined period of time (expressed either in a number of months and/or a percent of increase from original principal balance) after which any/all accumulated "negative amortization" (aka "deferred interest") is accounted for in a re-amortization of the loan balance over the remaining term of the mortgage at the then prevailing rate of interest. Amortization is also re-casted at each adjustment even if no negative amortization. Typically, any payment cap that would otherwise factor in is disregarded in the event of re-casting.