5 axis Cnc Router

Hi guys

I am new to this forum and Linuxcnc.
I have a big  5 axis Cnc router that just been fitted with a Linuxcnc controller. We are having a issue with the Machine, when running 5 axis simultaneously the machine is super slow but then running test G code the machine speed is absolutely fine. So we have established it can only be a problem between the CAM and the post processor. The first Post we used was an old one that did not have time inverse so I downloaded the latest one from fusion for Linuxcnc, and the guy who installed the system for me modified the post for me I haven’t tested it yet, but we have tested a G code sample that was running G93 and it did not work. If you guys have any input or knowledge of how we go about to solve this problem, I would be really great full.

another issue is every time the machine finished a job and the head does not return to 0 the machine will give me a joint mode error and it will loose the z 0 position aswell as the tool offset, so I need to home the machine every time?