November 2015: Minimal cutsets deleted when mixing frequency and probability events 
Running an analysis that generates a MCS with a mix of frequency and probability MCS could produce a uncomplete MCS list if you also use the ForceMinim (RiskSpectrum v1.2.1) or "Always perform forced minimisation" (PSA 1.3) setting. Ideally, you should avoid a situation with mix of frequency and probability cutsets. The possibility to generate a MCS list like this is not treated as an error as it is a legacy from some clients who wanted to use the frequency event as a multiplier, but we strongly recommend avoiding such modelling. RSAT issues a warning if the analysis case generates a MCS list with both probability and frequency cutsets. The interpretation of such analysis cases is problematic, because the interpretation of the top value is unclear. 
If you still want to generate a mix of frequency and probability MCS and use the 'Always use forced minimization' option you should also set the 'Low limit re-minimisation' to the number of cutsets. 
Fixed in 3.2.7 
RiskSpectrum Analysis Tools (RSAT)