In SAC, amortization monthly amounts will not be the same even for 360/360. In LAC, they will be. It is just how SAC (exponential) is calculated.
SAC formula is on help.sap. But essentially, in SAC calculation, all future cash flows are discounted using effective interest rate also known as YTM (yield to maturity). Since value of a $1M cash flow discounted to 12 months would be different than $1M discounted to 13 months, therefore resulting amortization will be different each month.
Also, regarding your DBT_E019 flow (Translation discount), I'm not getting it in my test. May be your Amortization procedure settings are different. Anycase, please compare with attached screenshots and see if it helps; and provide additional details if it does not.
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Mani