Installing NetBSD to an SD card on eBox

Hi,

I'm trying to install NetBSD 9.3 on an eBox (Vortex86MX A9111 CPU, 512 
MB RAM) to an SD card using the built-in SD card slot (the device's 
BIOS considers it to be an IDE hard disk drive; currently, I can use 
it to boot FreeDOS). I've written the NetBSD install image to an USB 
stick. It didn't reliably boot at first, hanging or rebooting at 
random moments, but works now after resetting the BIOS to what it 
calls "optimal defaults".

If I insert the card before turning the device on, the boot process 
loops with the following (or similar) message:

'wd0d: device timeout reading fsbn 0 (wd0 bn 0; cn 0 tn 0 sn 0), 
retrying'
rdcide0:0:0: lost interrupt
	type: ata tc_bcount: 512 tc_skip: 0

If I turn the device on without the card inserted and only insert it 
after the boot process has finished, I can use the installer, but 
can't actually install the system for the following reason: "I can not 
find any hard disks for use by NetBSD".

 From there, I've tried the following:

a. Utility menu -> Partition a disk -> Update device list, then Finish 
partitioning. When I do that, I reproducibly get a segmentation fault.

b. I can start sh. The output of mount only shows /dev/sd0a (it seems 
to be my USB stick) and tmpfs. Ejecting and re-inserting the card does 
not cause any new lines to appear in the output of dmesg.

How do I proceed?

Regards
Stanislav