Fluctuating Speed Controller

My home made mini bandsaw is powered by a 48VDC/10A power supply along with a PWM 1-50VDC, 40A Speed Controller and a 12-48VDC, 400W, 3K-12K RPM Spindle Motor(see links of these items below).

The saw is designed to handle small hobby projects (1/8” to 1/4” plywood but a few times I also use it to cut 1/2” plywood) and performs well except at times the speed seems to have its own mind like when I do a cut (always on 1/2” plywood) the speed decreases to almost 0 RPM and then I have to turn the knob on the speed controller up/dn until I find a good speed.

I know this is not a powerful bandsaw but I wonder which part gives me the problem, is it the power supply, the speed controller or the motor?

48VDC, 10A Power Supply
https://www.amazon.ca/gp/product/B07...?ie=UTF8&psc=1

10-50VDC, 40A PWM Speed Controller
https://www.amazon.ca/gp/product/B06...?ie=UTF8&psc=1

12-48VDC, 400W, 3K-12K RPM Spindle Motor
https://www.amazon.ca/gp/product/B07...?ie=UTF8&psc=1