So after about 12 forced power offs while copying data (via rsync) this is the only output from dmesg:

# dmesg | grep -i btrfs
[    0.776375] Btrfs loaded, crc32c=crc32c-generic, zoned=yes
[    5.497241] BTRFS: device fsid d9a2a011-77a2-43be-acd1-c9093d32125b devid 1 transid 389 /dev/sdc scanned by systemd-udevd (732)
[    5.521210] BTRFS: device fsid d9a2a011-77a2-43be-acd1-c9093d32125b devid 2 transid 389 /dev/sdd scanned by systemd-udevd (743)
[    6.743097] BTRFS info (device sdc): disk space caching is enabled
[    6.743100] BTRFS info (device sdc): has skinny extents
[   61.730008] BTRFS info (device sdc): the free space cache file (1833981444096) is invalid, skip it

Should I worry about the last line?

Thanks,
Richard