sounds like you pressing on the clutch isnt actuating the mechanism correctly.
If you try driving up to 5500rpm then lift but not touch the clutch pedal its easy for the lever to shift into neutral under no load.
Does the SMF replicate the distances etc of the OE clutch?
You may be (due to some incorrect or incompatible component)at the limit of your clutch adjustment.
I would also be looking at checking your clutch master cylinder fluid level, maybe bleed it, and maybe trying pumping the pedal a few times,then going 'ballls out' soon after to see if the change up 'works' as a result...
hth