Only one subvolume can be mounted after replace/balance

["Jakob Schöttl" <jschoett@gmail.com>]

Hi,

In short:
When mounting a second subvolume from a pool, I get this error:
"mount: /mnt: wrong fs type, bad option, bad superblock on /dev/sda, 
missing code page or helper program, or other."
dmesg | grep BTRFS only shows this error:
info (device sda): disk space caching is enabled
error (device sda): Remounting read-write after error is not allowed

What happened:

In my RAID1 pool with two disk, I successfully replaced one disk with

btrfs replace start 2 /dev/sdx

After that, I mounted the pool and did

btrfs fi show /mnt

which showed WARNINGs about
"filesystems with multiple block group profiles detected"
(don't remember exactly)

I thought it is a good idea to do

btrfs balance start /mnt

which finished without errors.

Now, I can only mount one (sub)volume of the pool at a time. Others can 
only be mounted read-only. See error messages at top of this mail.

Do you have any idea what happened or how to fix it?

I already tried rescue zero-log and super-recovery which was successful 
but didn't help.

Regards, Jakob