NBI NTA

The NTA of NBI has fallen from $1.99 to $1.80 per unit over the course of this week. There’s been no discussion as to the reasons. Does anybody know whether a fall in the NTA is due to bad debt write-offs and therefore irreversible or are there other reasons why the NTA might fall. I’m trying to determine whether I’m better cutting my losses now versus holding off for a recovery in time and I’m concerned that exposure to high yield credits in these times is a road to nowhere. Thoughts appreciated.
Rik