We use Pega Marketing , NBAA application on version 74.

When trying to re save an eligibility Decision table  - it is throwing the error for few when rules out of several hundreds available on decision table, nothing is captured in logs: stringlist of column comparisons—Instance of class Rule-Obj-When not found..Class..When**.

I verified WHEN Rules are available on the system, Revalidated the RSV in which these WHEN rules are present and everything was good. Enabled logger on when rules and DT rule, but couldn't find anything in logs. 

The when rules shown in error are recently added ones, to clarify this is an ongoing daily process we use and never have come across this sort of error.

Strings within DT or WHEN rules are also validated and looks similar to what we have done before over 100 of rules.

Any inputs are really appreciated.