Overdrive Light Flashing On and Off

I did a hard launch this morning, and when it got into 3rd gear or OD, I noticed the O/D light flashing on and off. I can definitely detect OD working (pushing the OD lockout button resulted in RPM rise, pushing again resulted in a drop in RPM signifying that the OD band was working). I can also detect the torque converter lockup in 3rd gear and 4th gear (as I commanded).

I don't have a code reader on me, but will this set a DTC?

The O/D light was blinking on and off the entire 20+ minutes. I haven't tried restarting the car yet.

I noticed several days ago that my car no longer coasts down. For example if I drop the throttle at 60 mph, normally I'd start to lose speed fairly quickly. Now, if I drop the throttle at 45+ mph, the car keeps coasting along longer than before. Is there any correlation? I am using the same coasting fuel shutdown settings as before, and I haven't touched anything related to the shift scheduling.

What I would like to know is if there is going to be any hard, physical damage to the transmission, or if this is an indication that it is just some minor malfunction/failure of a sensor. I understand it's going to be hard to diagnose without an actual DTC, but I don't have a code reader with me.

The last time I reflashed it was a few weeks ago. What was the code you pulled from the PCM?

It's a 2000 4R70W with 30k miles. It has about 3 full ATF changes and 4 filter changes and is currently using M1 ATF. I only noticed the light this morning.