Apart from NOK, another "N" stock as a potential bankruptcy candidate is NIHD.
NIHD is also related to telecommunications, and also had an ugly gap down in April.
NIHD December 2019, coupon 8.875%, yielding 10.60%
http://cxa.gtm.idmanagedsolutions.com/finra/bondcenter/BondDetail.aspx?ID=NjcwMjFCQUMz
NIHD April 2021, coupon 7.625%, yielding 10.07%
http://cxa.gtm.idmanagedsolutions.com/finra/bondcenter/BondDetail.aspx?ID=NjcwMjFCQUU5
NIHD is also related to telecommunications, and also had an ugly gap down in April.
NIHD December 2019, coupon 8.875%, yielding 10.60%
http://cxa.gtm.idmanagedsolutions.com/finra/bondcenter/BondDetail.aspx?ID=NjcwMjFCQUMz
NIHD April 2021, coupon 7.625%, yielding 10.07%
http://cxa.gtm.idmanagedsolutions.com/finra/bondcenter/BondDetail.aspx?ID=NjcwMjFCQUU5