Improve BBB USB write to file speed

I have cameras attached to a BBB wireless by USB (astrophotography cameras controlled by Kstars/Ekos) but I’m having trouble. The thing is both cameras work reliably for smaller data transfers, that is, if the “region of interest” is cut down to a small area. The smaller camera (a couple megapixels) will even work full frame so long as the exposure time is greater than one second. And both cameras work fine if the BBB is switched out for a Beaglebone AI.

So I’m wondering if there is a bottleneck along the path USB to storage in the BBB that could be alleviated. The BBB is running off a micro SD card (to provide storage for the photos). Does it matter how “fast” the card is? Would it speed up transfer to attach an SSD to a USB hub? Running the top command I don’t see any constraint imposed by the BBB memory or CPU.

It would be very nice if I could make this work and would appreciate any pointers. Thanks.