I am experiencing the same issue.
HAS mode works fine for the initial volley of two HARMs, after landing and rearming, the WPN sub-screen for HARMs never resets back to the grid -- it remains blank. None of the OSB buttons work, except the SRCH (OSB4). But even then, you can't change the TBL, so it's pointless.
If, during the landing and rearm, I shutdown the engine and everything entirely, when everything comes back up the HAS screen on the WPN sub-screen seems to be working, but unfortunately the radar sights never show up on the HAS screen crosshairs again. So I'm not able to select the radar sight to get a lock and launch. I've done everything I can think of to get the HAS screen to reset, including cycling the AG88 PWR off and on again. It doesn't help.
If during in-house testing you are able to launch the second set of HARMs after rearm, please share with us the sequence you go through to get the WPN screen to work again.
Version: 2.5.6.61527
Thanks and cheers!