It's all about the Software

Is there something special about 256k BW and certain serial numbers (or firmware) that won't work?
Ref Super Station #5
Airspy #2 and #3 will not work on 256k, but Airspy#1 works 100%.
Just put v3.4 on the site (old W7 Netbook so it's 32bit machine) this AM to see if that would help. To get the
firmware version, that would require a site visit 1:20 drive one way.

Board revisions are different for what that is worth.
{^_^}

Airspy SDR# Studio displays all the supported tuner bandwidths. 256khz is not supported on Airspy HF+ Discovery "CD" version.

https://ibb.co/j9MjYwzM