2025 LT cruise control weirdness

I’m driving a 2025 LT (Cummins X-15, Eaton 12-speed automatic), governed to 70 mph. It has a really annoying glitch: with the cruise control on, it’ll run at 70 mph for a while, then gradually slow down to 67 mph. I can accelerate back up to 70 if I step on the accelerator, but if I take my foot off, it slows back down.

The truck is governed to 70 for cruise on or off, and when it does the above, it won’t go faster than 67 unless the cruise is on.

I can often reset it by turning the cruise completely off and waiting a few seconds. Also, sometimes if I leave it alone it’ll eventually speed back up.

It’s a Ryder leased truck, and the young dude mechanic seems clueless.