Speed: Foward only filter is bugged

What is your operating system?
Windows 11 latest version

What is your Shotcut version (see Help > About Shotcut)?

Can you repeat the problem? If so, what are the steps?
When using the Speed: Foward Only, the speed just randomly starts going down on the dial and my computer with a 6 core processor just slows to a halt at the footage starts lagging. I have no other apps open.

“Dial” is meaningless. It implies some circular control. Please improve the description. Also, you need more steps. As this reads, all you did was add the filter and not make any speed changes.

slows to a halt at the footage starts lagging

Well, if you added a keyframe whose value is less then 1.0 it is supposed to slow and “lag” (whatever that means).