It looks very much like the frame timing bug that got fixed in later Unity versions.
As you can see, the framerate isn’t just spiking, it’s doing a heartbeat monitor thing where each spike is followed by a dip.
The very simple explanation of what’s happening is that the game’s able to run at 60 fps, but bugs in how the timing is calculated leads to the engine believing that one frame is taking longer than it does, and that the next is taking shorter than it does.
This does lead to slight visual stutter, as the delta time values for the two frames will not be 1/60, but values slightly above and below. This means that every single system that relies on deltaTime (like animation and whatnot) will have visual glitches.
The last image in [this post]( Time.deltaTime Not Constant: VSync CameraFollow and Jitter page-4#post-4312405) is an excellent visual explanation. There’s also an older blog post about this here, and as you can tell from that it’s not a Unity-exclusive problem.
Since the delta time change is pretty large, I doubt it ever got backported to 2019, so sadly I assume that the only way you can deal with it is to update to 2020.