New to mach3 and CNC, have issues with spindle speeds

Hi guys.

I just started getting into CNC not too long ago. Struggled for the longest time to get the inverter set up correctly with the spindle but thanks to the great help of the forum I have finally managed to get the machine running. The struggles have been chronicled here:

https://www.cnczone.com/forums/spind...cnc-forum.html

Anyways, my next challenge now is to connect Mach3 to my spindle and control speed. I have succesfully managed to switch on the spindle with a relay and speed can be controled. I have set the minimum frequency of my inverter to 120Hz and max at 400Hz. When I switch the spindle on in mach3, it ramps up to the displayed frequency. However, once I increase the frequency above roughly 270Hz, it will not go below it. That gives me a spindle frequency range of 270-400Hz only. The strange thing is that if I started it at 0% which is 120Hz, it will remain at that frequency and anything below 270Hz I will be able to go back down to 120Hz. After I increase the freq and come back down to 270Hz, the speed fluctuates when it is around 270Hz.

I have done no setup to mach3 spindle settings, don't really know where to start. Would appreciate any help in this issue.