Hi Rains
The Profoto Compacts have always had a standard flash duration of 1/850s - which while is fast compared to some other strobe units - is not fast enough to freeze razor-sharp action images.
Is there a site that actually says that the compacts are able to freeze action?
When you're shooting with Compacts, try and not bump the settings to more than 1/4 or 1/3 of the full power (so from 1 to 10, try not to go past 2.5 or 3).
Most flash generators & monoblocks work the same way, the lesser the power, the faster the flash duration...
More importantly - if you're going to freeze action, there are 3 things to get right first.
I'm assuming you have a manual DSLR.
1) Get rid of ambient light.
2) Make sure your shutter is not at 1/60 or 1/45. Should be at least 1/125 or go to the max that the camera allows.
3) Shoot only with that one light (compact 300) and make sure that there is no other flash firing as a slave - unless it's faster or same speed.
The reasons for asking you to take these steps are 1) the ambient light (if still around and at the same power of the strobe) will continue to light the subject after your main strobe has popped. This will result in light trails behind the sharp exposure - also known as movement blur.
The shutter speed should not be too slow because if you keep it open - you're allowing the exposure to continue to accept ambient light (which leads to tip #1).
If you have another flash that has a slower duration, that again will continue to light the subject after your main flash and will show up as a second line or in some cases a blur.
Try to get these conditions right and let us know if you experience an improvement in the shots...