I was able to resolve the issue by following the steps below:
1. Stopped the server.
2. Reset Stack Size Multiplier to correct value (in my case 5.0)
3. Restored a backup prior to 312.14 patch (I restored a backup from around Jun-30, 8:00am UTC).
Everything back to normal (stacking limits and stacks of items in storages).
great but not sure how to restore to a backup...shouldn't have to do anything. pay for a server that i have to reset due to an "update"