This appears to be true given this memo from the GAB on April 14th,
"We are receiving information from some county clerks who use [PROM] packs with tabulating equipment for their voting systems, and they report that they are unable to get sufficient additional [PROM] packs from their respective vendors to conduct the recount, while at the same time preserving and retaining intact the Election Day prom packs.This is absolutely unacceptable, and it's just another example of a real issue with our election systems in Wisconsin.
...This may mean getting judicial permission to clear memory devices for reuse during the recount"
Update: (4:07pm) The candidates have agreed to a hand recount in these 31 counties. No erasing will be done. Thank God!
Update: (5:28pm) I posted more information here.