Is this something to be concerned about?
Netgear Nighthawk X4 D7800
OpenWrt 19.07.2 r10947-65030d81f3 / LuCI openwrt-19.07 branch git-20.057.55219-13dd17f
Sat May 2 03:51:33 2020 kern.err kernel: [ 19.629036] print_req_error: I/O error, dev mtdblock0, sector 0
Sat May 2 03:51:33 2020 kern.err kernel: [ 19.629486] print_req_error: I/O error, dev mtdblock0, sector 8
Sat May 2 03:51:33 2020 kern.err kernel: [ 19.634231] print_req_error: I/O error, dev mtdblock0, sector 16
Sat May 2 03:51:33 2020 kern.err kernel: [ 19.640093] print_req_error: I/O error, dev mtdblock0, sector 24
Sat May 2 03:51:33 2020 kern.err kernel: [ 19.660003] print_req_error: I/O error, dev mtdblock0, sector 0
Sat May 2 03:51:33 2020 kern.err kernel: [ 19.660031] Buffer I/O error on dev mtdblock0, logical block 0, async page read
Sat May 2 03:51:33 2020 kern.err kernel: [ 19.669799] print_req_error: I/O error, dev mtdblock0, sector 0
Sat May 2 03:51:33 2020 kern.err kernel: [ 19.672018] Buffer I/O error on dev mtdblock0, logical block 0, async page read
Sat May 2 03:51:34 2020 kern.err kernel: [ 19.679044] print_req_error: I/O error, dev mtdblock1, sector 0
Sat May 2 03:51:34 2020 kern.err kernel: [ 19.685734] print_req_error: I/O error, dev mtdblock1, sector 8
Sat May 2 03:51:34 2020 kern.err kernel: [ 19.691524] print_req_error: I/O error, dev mtdblock1, sector 16
Sat May 2 03:51:34 2020 kern.err kernel: [ 19.697514] print_req_error: I/O error, dev mtdblock1, sector 24
Sat May 2 03:51:34 2020 kern.err kernel: [ 19.703971] Buffer I/O error on dev mtdblock1, logical block 0, async page read
Sat May 2 03:51:34 2020 kern.err kernel: [ 19.711809] Buffer I/O error on dev mtdblock1, logical block 0, async page read
Sat May 2 03:51:34 2020 daemon.err block: No "mount.ubi" utility available
Sat May 2 03:51:34 2020 daemon.err block: mounting /dev/mtdblock6 (ubi) as /mnt/mtdblock6 failed (25) - Not a tty
Sat May 2 03:51:34 2020 daemon.err block: No "mount.ubi" utility available
Sat May 2 03:51:34 2020 daemon.err block: mounting /dev/mtdblock7 (ubi) as /mnt/mtdblock7 failed (2) - No such file or directory