I don't know if this is somehow a related issue, the call waiting feature is no longer working correctly on my HT-502.

I can flash from a conversation to second caller but can no longer flash back to the first caller, nor can I then flash/return back to the second caller. In this case I lose both callers. I had this problem with the HT-286 but HT-502 corrected this issue. Now for some reason the HT-502 seems to have this problem.

My HT-502 still has the original firmware.