The gun refusing to fire when the trigger is pressed, when it would fire before, is usually a bolt stick issue. It usually occurs when you attempt to fire the gun after a brief period of no firing. I suspect if you use the next larger carrier size, this problem will go away.
When it won't fire at a lower velocity but does at a higher velocity, is usually due to using a bolt spring that is too stiff. If you happened to use a different barrel, the changing pressure requirements will change the lowest velocity that the gun will cycle at. You may have to use a different bolt spring or cut one to suit your barrel needs.
The shooting hot issue when it was chronoed lower, is usually related to the regulator seat oring leaking. A small leak will often produce a hotter first shot, but subsequent shots in rapid succession will be around the preset velocity. If every shot is hot, then something has changed. It could be that something wasn't completely seated when you first chronoed and then settled into place or it could be that something is interfering with the movement of the regulator piston assembly. Clean the cavity out in the back in case a piece of dirt or sand has gotten stuck in there. A complete clean of the valve wouldn't hurt for the same reason. Its a quick and inexpensive thing to do and usually fixes most problems.
Given that your gun is a classic RT, the springs that push on the regulator piston are probably weaker. That combined with a higher pressure release of the piston assembly means that the chamber pressure may not get high enough to cause the regulator piston assembly to vent air out the back. I wouldn't worry about that.
In review, I would clean first. Then I would tune my level 10 setup again.
Except for the Automag in front, its usually the man behind the equipment that counts.