Yun vfat partition corruption, Openwrt won't run dosfsck

Five years of Yun’s and half dozen working and a new problem popped up. Randomly, at start-up, a sketch will attempt and fail to write (csv) to the mnt/sda1/arduino/www partition. I can have dozen or a hundred previous files on there and if during the new boot, openwrt detects a file corruption problem, instead of trying to fsck as it does on the ext4 partition, it says
"check_filesystem: /usr/sbin/dosfsck not found and sets the partition to read-only.
From then on the sketch won’t write anything, throws file not found error, and an hour later I come back to retrieve a data file and nothing.

I can remove the SD, put it in an adapter let Windows do a file check, it complains that it needs to unmount, which is OK’d, It completes the operation and then I can replace the SD card, restart the Yun and the sketch will write again as it should.
I use WINSCP to access the SD and it can advise me that the partition is read-only but cannot fix it.

I would like some help to compose and run a python script (using Process ) that could do an on-the-fly repair if the file error occurs. I have found a few suggestions in the Openwrt forum but can’t completely comprehend all the operations as I am NOT a Linux buff.
https://github.com/openwrt/packages/issues/7826
ALSO This: which addresses the exact issue
https://www.mail-archive.com/openwrt-devel@lists.openwrt.org/msg48916.html

I have typically found the LOG entry below in the Yun system log so I can tell it ordinarily should try to correct the corrupted partition. I have always used the Yun SD card expansion sketches and they are different for Rev0 and Rev2, but recently both versions, Original 2015 Yun and later Rev2 2018 Yun have had this hiccup. I do have an original 2015 Yun in service in the field for almost 5 years that has never exhibited this fault.
I suspect it has something to do with the OpenWrt load but they are different on Rev 0 and Rev 2 So can someone offer a solution? I cannot find any missing Openwrt packages, is installed and up-to-date the installer reports.

(Error Booting - my comment)
Thu Apr  9 21:09:34 2020 daemon.err block: /dev/mtdblock4 is already mounted on /rom
Thu Apr  9 21:09:34 2020 daemon.err block: /dev/mtdblock5 is already mounted on /mnt/mtdblock5
Thu Apr  9 21:09:35 2020 daemon.err block: check_filesystem: /usr/sbin/dosfsck not found
Thu Apr  9 21:09:35 2020 daemon.err block: /dev/sda2 is already mounted on /overlay
Thu Apr  9 21:09:35 2020 kern.warn kernel: [   69.135333] FAT-fs (sda1): Volume was not properly unmounted. Some data may be corrupt. Please run fsck.
Thu Apr  9 21:09:41 2020 kern.err kernel: [   75.248738] FAT-fs (sda1): error, fat_free_clusters: deleting FAT entry beyond EOF
Thu Apr  9 21:09:41 2020 kern.err kernel: [   75.251588] FAT-fs (sda1): Filesystem has been set read-only