S42C Non functional at speeds above 150mm/s

[KevlarBandit]

I purchased two S42C stepper+drivers and whenever I run them at a speed above 150mm/s (about half the speed the need to run at) they stutter terribly such that they can't even print in a straight line. They stutter even with no load. It appears to me that this is due to the calibration not setting appropriate settings for higher speeds. As it stands, unless this is able to be fixed by an end user (or will be fixed by biqu themselves) I will highly recommend no one purchase them as they are not fit for purpose.

So, I have three questions. One, how do you set them to open loop mode, two, where is the firmware for them. I've seen the s42B firmware but the page that I have been told contains the s42C firmware does not contain any firmware, only manuals and 3d models. If the s42B firmware is the same firmware as what is running in the s42C, a confirmation on this would be excellent.
Finally, how do you flash the firmware.

As it stands, I need answers to all three or there is no point in helping me. I need the open-loop mode to verify it isn't some other issue, the firmware to try and fix the problem and a way to flash the firmware.

I will also note, I know of at least two other users who have experienced the same issue as I did with the s42C. Which means that every single person I have talked to who has ran them has the same problem or runs their printer at such a slow speed that it is a non-factor. No, running the printer at slower speeds is not an acceptable solution. I would sooner toss the drivers in the bin.

I have previously tried to get assistance on this matter through the email support but, and I quote, got "00" as a response. That was the entirety of the response and follow up emails got me no further response. It took a week to get that response.