Additional log files being created and failing integrity check

Please forgive
a) if posted in wrong section
b) my ignorance

For the last few versions I have been unable to easily update Nextcloud.
Every time I log in I get the:
[There were problems with the code integrity check. More informationā€¦]

When trying to upgrade I get the following:

Results

  • core
    • EXTRA_FILE
      • nextcloud.log
      • core/ajax/nextcloud.log

Raw output

Array
(
[core] => Array
(
[EXTRA_FILE] => Array
(
[nextcloud.log] => Array
(
[expected] =>
[current] => 82016bf1e4024ace1eb98d14f277ee0b6350079f283deca918c2c4205c4c018caa4a936c62ffc2e0d1e7da5ec4f481d33ef7dea69e8f8dc85ef2d813f3b434cf
)

                [core/ajax/nextcloud.log] => Array
                    (
                        [expected] => 
                        [current] => 4ad617d3cef65c24e82a077d9c7e27aa4a74763fef9583c0eceff23ea333c8bb1ec3b740ed5a554be634f97cafb4ff4564c790797d95b2ec52df5e2954793925
                    )

            )

    )

)

Does anyone know:
What these additional logs are for
Why they are created
why they fail integrity check
(most importantly) How can I fix this problem.

Vital statistics:

Nextcloud

Version: 14.0.4.2
Apps installed: 46
Apps updates available: 0

PHP

Version: 7.0.32
Memory Limit: 512 MB
Max Execution Time: 3600
Upload max size: 511 MB

Database

Type: pgsql
Version: PostgreSQL 9.5.14 on x86_64-pc-linux-gnu, compiled by gcc (Ubuntu 5.4.0-6ubuntu1~16.04.10) 5.4.0 20160609, 64-bit
Size: 194.3 MB

Any more info required, please ask.
Thanks in advance