Ryobi ETS 1525 Table saw

[greengrass]

Ryobi ETS 1525 10" ( 250mm) table saw.
Testing squareness of cuts.

Standing a combination square against the blade and turning find the blade runs square and has no buckle.

Checking the fence to blade alignment by placing the square against the fence and just touching the blade at the rear and sliding along fence to front of the blade finding a gap of around 2mm

Checking the mitre slot by the same method sliding the square along the mitre channel in the table top. Facing the working front of the machine the left slot shows 2mm out at front while the right hand one (obviously ) shows 2mm out at rear of blade.
Seems to me as I've not checked this before until needing to make exact 300mm with cuts of panels it's either a rough cut saw or someone hasn't done the 'Square up' properly, or the motor unit has moved.

Q: Am I testing the squareness of my table saw blade and cut correctly or not? I've approached Ryobi with this 'Out of true ' problem and they just tell me to take it to a service centre, that's not cheap.