Same issue on the C27CHG70. I recorded a slow-motion video with my cell phone showing this problem while playing Mirror's Edge: Catalyst, seen here: https://youtu.be/np6yxsNzj8E
C27CHG70 with DisplayPort, firmware 1020.0
Freesync Ultimate Engine
ASrock Vega64 GPU with drivers v19.1.1
There's no issue with Freesync Standard, but then the variable refresh range is much worse and no HDR is available. This monitor was expensive - please fix this, Samsung!
I am really bored and annoyed about that, I begin to seriously hate Samsung because I wrote them a lot of emails to complain about that, without any response from them. I fell like they think I am stupid and I really don't like that. They always say they transmit the issue to the technical service, I wait for months and write again, they say "oh sorry" and the same thing repeats and repeats.
So I plan to sell the monitor and buy an AOC AGON AG273QCX, it is far better, more expensive but really better, and the overdrive is controllable.
It's really bad that Samsung ignores this problem. Currently this screen simply has a mode Freesync 2 useless in the state. As a result, I am forced to use the simple "Freesync 1" mode.
Unfortunately, standard Freesync is entirely useless to me (and doesn't even eliminate the problem entirely) because I love HDR in games. Everything else about this monitor is amazing, except for the auto sharpening effect when using HDR (which support confirmed cannot be turned off, unfortunately). It's such a same that this monitor is ruined by something that is easy to fix, all they would have to do is make the overdrive setting adjustable.
The lack of support for this is absolutely horrible, even more so for a product priced at $600 USD (for 27 inch). I have gotten better support with $150 USD monitors than I have with this monitor. Even a support rep saying that they aren't going to do anything about it would be better than complete silence.
I have the same issue on my C27HG70 and it renders the "ultimate engine" completely useless for nearly all applications.
It is a shame on an otherwise competent monitor but since Freesync was one of its major features and it is a gaming monitor I've had to adjust my reviews from a strong 4 to a mediocre 3. Mind this is not a cheap monitor and expectations should be high. You can get many other 1ms 144hz monitors with working Freesync for the same price, although IPS-panels.
I've always held Samsung in high esteem but it appears they can't do gaming monitors and have no interest whatsoever to fix the issues. My next monitor will certainly not be a Samsung if they can't even bother to give us an option to turn off the overdrive (which at least would be a half-decent fix).