[SELF-RESOLVED] Can't factory reset/hard reset Pixl.js

The instructions say:

Hard Reset To clear out all saved code, reset Pixl.js while keeping
BTN1 held for around 10 seconds (even while Pixl.js says SELF TEST
Release BTN1).

Once Pixl.js displays Removed saved code from Flash you can release it
- this will clear out any previously saved code and bonding data that could have caused problems.

Note: If you release BTN1 when instructed by the text Release BTN1
then a self-test will be performed. Saved code will not be loaded from
flash, but will not be erased from flash either - a subsequent reset
will start Espruino up loading the saved code as normal.

However, when I repower the device with BTN1 held down, I see the board go into bootloader mode, as it tells me that I should RELEASE BTN1 FOR DFU. I continue to hold down BTN1 for 10 seconds, but once the progress bar gets to the end, it just prints out READY TO UPDATE and not SELF TEST. Please help because I've basically bricked it (can't access Bluetooth btw)!

Before the problem, I overwrote the splash screen to be

require("Storage").write(".splash","");

I also ran

E.setConsole("Bluetooth");

at startup, and wrote code to the device using the 'Direct to Flash (execute code at boot, even after 'reset()') - USE WITH CARE' option. The IDE warns me that it's hard to recover the device when code crashes, but I originally ignored it.

Many thanks,
-James.