I’ve not seen this particular issue, but BTRFS is a turd on NVME. It does about 2/3 to 1/2 the IOPS of EXT4 or XFS on several PCIe 3.0 and 4.0 drives I’ve tested on several modern AMD and Intel systems. XFS actually has the upper-hand on NVME performance over EXT4, but not by much.