I didn’t enter an Other Assets balance. Why did one appear?
By default, the program reinvests minimum distributions in the Other Assets. If you want to model a case in which minimum distributions are spent, see Input Assumptions.
Also, you may have instructed the program to pay Roth IRA conversion taxes from the Other Assets in the Quick Roth IRA Conversion calculator. If so, the program created a balance large enough to pay those taxes.