For money being distributed from a DC plan after age 70-1/2:

1. If the distribution was less than the minimum required under 401(a)(9) in a previous year (say 1996), does that affect the minimum required in the current year (say 1998)? Does the answer to the previous questions change if no excise tax has been paid on the inadequate distribution?

2. Assume that nobody can reconstruct the minimum distribution methodology used in prior years (single or joint life, recalculate life expectancies or not) because data is unavailable. What rules govern the methodology to be used in the current year?

see 1.402©-2,A-7

If min distrib required for a calendar year is not made by the end of the year,it is added to the minimum distrib due for the next calendar year to determine the amount that is ineligible for rollover

not sure if that is what you are looking for.
See also Q & A 79 under plan defects
APRSC might apply, depending on facts