QCA9984 5g reception

Hi, I have an MR52 flashed with 23.05.0 using the default ath10k-firmware-qca9984-ct.
I have a problem with the QCA9984 5g radio (radio1). It shows up in wireless scans from other devices, and with good signal strength. However, channel analysis on the MR52 itself shows no detected stations on radio1 and clients are unable to connect to a configured station on that radio and nothing is logged on the MR52 when they attempt to do so. There's another 5g AP right nearby, with strong signal, and this MR52 doesn't even see that.
Is this likely to be defective hardware? Would a poor receive antenna (pigtail connection) be enough to cause this?
Both the other radios (dual band scanning radion and 2g) function as expected.

I am wondering what I might try before I finally give up on it.
Many thanks for any suggestions I might try.