What might be making my exercise bike so noisy?

My exercise bike often makes a ton of noise, including grinding, rumbling, clicking, rattling, and loud knocking.
Are there any obvious likely culprits?  Bearings, lubrication, alignment, fractures? Something else?
I’d sure appreciate any thoughts!

Additional notes:

* When I abruptly stop pedaling, the flywheel of course continues to spin, but the troublesome noises stop.
* The crank arms appear to be securely attached to the axle, I don’t think the pedals are generating the noises, and the belt tension seems fine.
* [Here](https://www.youtube.com/watch?v=d2xqdHJKjMc)’s a version of the video with the hum of the freezer in the background roughly filtered out.
* The bike is a Schwinn 170 upright (2016 model). The assembly manual is [here](https://download.bowflex.com/supportdocs/AM_OM/Schwinn/SCH.170.MY16.AM.OM.WARR.EN.pdf). I don’t see a service manual for this model, but the following year’s model (which is similar) does have one, [here](https://download.bowflex.com/supportdocs/AM_OM/Schwinn/SCH.170.MY17.SM.EN.pdf).