Cannot create second rsync snapshot on multi-device BTRFS

[ppp7032]

Describe the bug
I have created an initial manual rsync snapshot of my ext4 root filesystem (on an LVM lv) onto my extra drives, which I have set up as a multi-device BTRFS filesystem consisting of RAID0 data and RAID1 metadata. If I click on Settings then click Okay (changing no settings), I am no longer able to create another snapshot as it says "Not enough disk space (<1,000 MB)". Closing and re-opening the app lets me create additional snapshots again.

To Reproduce
Steps to reproduce the behavior:

1. Click Settings
2. Click Okay
3. Try to create a snapshot

Expected behavior
The app does not erroneously report low disk space and allows me to create additional snapshots.

Screenshots

System:

• Arch Linux
• Cinnamon v6.4.10
• v24.06.6

[ppp7032]

The same issue arises upon trying to manually create a snapshot if it attempts to first "Calculate snapshot size" or something like that. This is also fixed by restarting the app and trying to create said snapshot again.

[siltal]

same issue,but all devices partitions are btrfs

[MikeB5027]

This looks similar to my issue #37: timeshift: "not enough disk space" when destination is btrfs raid1
Is the device shown in the bottom-right corner of your main timeshift gui always the same?
I find it picks the wrong BTRFS device when going into Settings and then says there is no space.

[ppp7032]

@MikeB5027 But if it picks the wrong device going into settings then I don't see how it would fix itself by simply restarting the app.

[MikeB5027]

It always picks the right device when I open it to do a snapshot, but it picks the wrong device if I go into Settings.
I don't know why - maybe it just uses the device in the config file when it is first opened, but does something wrong when Settings is selected.