Cannot fix btrfs errors after system crash

["Niccolò Belli" <darkbasic@linuxsystems.it>]

Hi,
I was trying to use AMDGPU-PRO's OpenCL stack (with the mainline 4.12.13 
kernel) while it suddently crashed the whole system, not even magic sysrq 
keys did work anymore.
With no surprise, at the next reboot I found several btrfs warnings (see 
https://paste.pound-python.org/show/S5zBG2tXZUTLG699saE5/).
Since btrfs scrub didn't find any error I decided to reboot into a live usb 
and start a btrfs check (I'm using btrfs-progs 4.13).
It did found lots of errors indeed (see 
https://paste.pound-python.org/show/IPxh9sly0EEb0MKPi2dw/).
So I made a full backup with dd and I started a btrfs check --repair (see 
https://paste.pound-python.org/show/c9AlT8ehKKJy6l5xhzXk/).
I also wiped the space cache with --clear-space-cache v1.
A subsequent btrfs check revealed it indeed fixed lots of errors (see 
https://paste.pound-python.org/show/1m2Wodd1q3n0eRlxLpZB/), but 
unfortunately i still have the following errors:

unresolved ref dir 7450239 index 2 namelen 6 name 431886 filetype 1 errors 
80, filetype mismatch
unresolved ref dir 7450595 index 2 namelen 6 name 431886 filetype 1 errors 
80, filetype mismatch
unresolved ref dir 7457122 index 2 namelen 6 name 431886 filetype 1 errors 
80, filetype mismatch

I'm already quite satisfied to be honest: two years ago repair used to eat 
my data, making things worse.
Anyway, why didn't btrfs-check repair them? Is there anything I can do to 
fix them?

Thanks,
Niccolò