Rakuten NISA gone, cost basis changed

Have some investment in Rakuten, in one US company, which is giving warrants as dividends.

Investment before dividend date:
1, around 100 shares 26usd cost basis, normal account
2, around 300 shares 23usd cost basis, NISA account

After dividend record date, dividend date is 7th (by the way they handle it as spinoff):
Friday:
Cost basis changed to 16 USD, everything in normal account
Saturday:
Cost basis changed to 0.00 USD

Did anyone experience something like this?
Wrote them an email, but wondering what will happen.

by ZaGaijinPremium