[users] New Baofeng GT-3TP won't transmit 450MHz up

I just received a box of new GT-3TPs, and programmed them with CHIRP to my standard settings. But apparently they won't transmit in GMRS freqs, where I have both ham and GMRS licenses.

In CHIRP Other Settings, here are the settings:

UHF Lower Limit (MHZ) 400 UHF Upper Limit (MHz) 600 UHF TX Enabled check

I reset one HT to factory and experimented with the rig bone stock. For it and the whole box of HTs. the highest they will go is 449.995MHz. Above that, the PTT button just beeps, as if the keyboard lock were on.

Is this some new restriction? Can I use CHIRP to get around it?