Showroom Prosimu T1000 PRS200 3DOF

I dont want to disappoint you. What you had described might have to do with your rig configuration rather. Fyi, not sure if you have watched Barry's youtube review on D-Box (with 4 actuators on the corners).
The guy, whose ID is anasmak11, in comment section of Barry's review (who owns a racing center having both 2-actuator and 4-actuator d-box systems), said that he and all his customers feel that 2 actuators system is much better and far more realistic than the 4-actuator system. IRacing forum users seem conclude the same. That got me to think twice. Per theory and math, as you probably know by now such 4-actuator configuration probably cannot accurately produce 3dof motion with simtool, which is based on calculation of 6x drivers for 6dof, generalizes to n drivers for nDoF.
SimTool allows you to assign any dof to any axis with arbitrary weight, as long as you configure rig as n drivers/axises for nDOF (2x for 2dof, 3x for 3dof, 4x for 4dof, 5x for 5dof and 6x for 6dof ——- topological Stewart platform), in which the axises are totally free and independent each other so they can freely move. The 4x for 3dof will not work properly because the 4 actuators/axsises are constrained (not free/independent), by which you cannot produce a combination movement with roll/pitch/heave. If try, often you get one leg lift up or other legs move too far (long). For an example, say 4x D-box config, let’s fix 3 actuators’ positions at zero. In other words, send zero to them. Now, try to move the 4th actuator in any of amount x while keeping other three at zero. You will fail on this trial. Now, for 3x case, you would not have this problem. You can freely move any one of thee actuators and independently regardless others. You can send arbitrary values x1,x2, and x3 to the actuators, they will accurately reach there (pitch/roll/heave positions). Although 4x for 3DoF mathematically possible, but it would be far difficult to implement.

For 3Dof motion, only need 3 actuators (motor). Adding extra one will cause actuators struggle for 3dof, and cannot reach to accurate positions (pitch/roll/heave positions). As anasmak11 said, he sticks with 2-actuator configured system (2dof). Similarly, using 7 actuators will not produce 6dof motion properly with SimTool.

Update: I watched the PRS200 T5 video. I can see such concern I have. You may change the configuration to 3 actuators, like the one shown below, thus all three actuators will be independent with no restriction that would gain all the resolution back, reproduce 3dof motion correctly/accurately from your SimTool data feed. You may put two on back and one at mid of front. The mid front one connect to a ball joint fixed on ground. Now you are able to yield a combination of roll/pitch/heave motion, just like shown below. Feel more nature on high speed cornering.

For detals, see my comments at:
https://www.isrtv.com/forums/topic/27998-seat-mover-vs-dbox-noseat-mover-dbox/