(Wrote this as I was working it out, so...)
Trying to update Bootloader from v0.42 to v0.47 (in Chrome). The status at the bottom of the browser says it's removing the boot and then adding the new one but almost immediately the status on the browser disappears. On the bangle itself it just save "Uploading boot..." with the progress bar set very early. I let it sit for a pretty long time (like an hour) and no change.
Had basically the same issue trying to update Messages app too.
Never happened to me before, not sure... what to do. Dis/reconnecting continues to show me both apps need updating.
And it seems that the Messages up disappeared (it shows in the apps list on the watch but then says it's not there if I try to access it).
Restarted the watch and now it says "Storage is corrupt" "Erasing Storage Area"... and hangs... Looking that up I saw someone else reported a related issue that I noticed the other day where my watch seemingly out of nowhere reverted its time to the unix epoch and UTC timezone. Didn't think much of it, but I guess it was precursor/related to whatever is going on now... perhaps that corruption issue from the previous firmware version.
After like an hour or so (maybe sooner I walked away), it got to a screen that just said Bangle with the watch image (I guess this is what you get if you have no bootloader anymore?). Then I could connect again and I had no apps. It seems to be letting me re-add apps again, so maybe things are ok. Think I lots all my preferences, but that's fixable.
So no help needed, I started this before I had it resolved, and now I figure I'll post just in case anyway else ends up searching some of these phrases.