Could this have something to do with this issue?
Mar 6 19:59:21 tdm emhttpd: shcmd (83): xfs_growfs /mnt/disk1
Mar 6 19:59:21 tdm kernel: xfs filesystem being mounted at /mnt/disk1 supports timestamps until 2038 (0x7fffffff)
Mar 6 19:59:21 tdm root: xfs_growfs: XFS_IOC_FSGROWFSDATA xfsctl failed: No space left on device
Mar 6 19:59:21 tdm root: meta-data=/dev/md1 isize=512 agcount=32, agsize=137330687 blks
Mar 6 19:59:21 tdm root: = sectsz=512 attr=2, projid32bit=1
Mar 6 19:59:21 tdm root: = crc=1 finobt=1, sparse=1, rmapbt=0
Mar 6 19:59:21 tdm root: = reflink=1 bigtime=0 inobtcount=0
Mar 6 19:59:21 tdm root: data = bsize=4096 blocks=4394581984, imaxpct=5
Mar 6 19:59:21 tdm root: = sunit=1 swidth=32 blks
Mar 6 19:59:21 tdm root: naming =version 2 bsize=4096 ascii-ci=0, ftype=1
Mar 6 19:59:21 tdm root: log =internal log bsize=4096 blocks=521728, version=2
Mar 6 19:59:21 tdm root: = sectsz=512 sunit=1 blks, lazy-count=1
Mar 6 19:59:21 tdm root: realtime =none extsz=4096 blocks=0, rtextents=0
Mar 6 19:59:21 tdm emhttpd: shcmd (83): exit status: 1
Mar 6 19:59:21 tdm emhttpd: shcmd (84): mkdir -p /mnt/disk2
Mar 6 19:59:21 tdm kernel: XFS (md1): EXPERIMENTAL online shrink feature in use. Use at your own risk!
It seems when the xfs_growfs doesn't have enough space on the disk, the shrink feature kicks in.