Sage released fixes for this March 2nd on KB 108946.
CI6000T for Sage 100 versions: 2020.0, 2020.1
CI6001T for Sage 100 versions: 2019.3-2019.4
The problem is fixed for the upcoming Sage100 2021 release scheduled for April.
To identify the items with zero average cost updated, Sage has attached an Inventory Detail Transaction Report modified to select Average Valuation Items where the Cost was $0.00.
Sage also a List of Steps to correct the cost on the items and the G/L costs posted.