Hi @chriscic42 ,
Without some more specifics about what you're doing (e.g. steps and or data table -- can be anonymized), it's hard to figure out the issue you're coming across.
However, when I try on one of my data table to run the Stepwise Fit personality under the Fit Model platform and select K-fold Crossvalidation from the red hot button, it runs just fine using the Max K-fold RSquare for the Stopping Rule. Also, are you using a crossvalidation column?
If you can provide screenshots of the steps you're doing or the data table with the script that reproduces the issue, it would help a lot to figure out what's going on in your situation.
Thanks!,
DS