It's a double whammy scenario: (1) high/rising inflation is...

It's a double whammy scenario: (1) high/rising inflation is eroding the value of fixed bonds (NBI owns fixed rate bonds); (2) in the commercial fixed space, people are worried some economies are facing the prospects of slowed growth and possibly even a recession (e.g., Great Britain). Therefore, there are worries some companies that issued junk bonds might not make coupon payments. Government bonds, by contrast, tend to be impacted by inflation only (well, emerging market bonds are a different story).

I also suspect a non-trivial number of holders of NBI are relatively older people, perhaps retirees, and years of ultra-low cash rates have pushed them to seek returns from assets that are actually too risky for their temperament/situation. They might be selling in disproportionate numbers. Finally, I'm not familiar with many analysts suggesting that it's time to get back into high yield bonds; that might be a signal that it's time to get into high yield bonds ; )

NBI is currently trading at an approximately 20% discount to NTA; it usually trades at between 8 to 12% discount, well, ever since the Covid19 crash. Pre-covid, NBI tended to trade closer to NTA.