Older Radeon card, 144Hz FreeSync monitor, reverts to 60Hz after game

Feb 25, 2019
I have an R9 290 and just recently got a 144Hz monitor for the first time. It supports FreeSync, which I of course turned on. But I noticed some odd behavior:

1) After coming out of a game or even a benchmark (like, say, Furmark) which was running well above 60 fps, the monitor reverts to a 60-65Hz refresh rate. Windows (Win7 64 bit) still says it's at 144Hz.
2) Changing refresh rates is usually ok, but sometimes it decides to hang at a black screen and force a restart.

I tried disabling everything that could be considered an "overlay" (Steam, F.Lux, etc.) but it doesn't seem to help. Also tried with a couple of different drivers (currently 18.9.3, not the latest from a recent rollback for other issues).

Anyone run into anything like this before? Hard to even know how to word it for a google search...
Couple addendums:
1) Using the DisplayPort output on the 290
2) No other monitors attached (there's a DVI cable attached to the card but it's not hooked to anything, other monitor died on me)
3) Latest stable and optional drivers both haven't helped.
Using Windows 10 myself and a display port R9 290X samsung monitor attached but I did not see this behaviour. Sometimes I see some things which I find odd but nothing like this the monitor displays as being 144hz all the time.

Monitor driver correct? Windows can be really weird sometimes regarding this (you can run it on generic monitor but that does not always work out).