Err:14 https://uk.mirrors.fossho.st/armbian/apt focal/main armhf Packages              
  File has unexpected size (516030 != 453208). Mirror sync in progress? [IP: 82.145.63.161 443]
  Hashes of expected file:
   - Filesize:453208 [weak]
   - SHA512:2106846c18399ffc28b2da849488e65c512fdc5024e395233874da288a0f8bcd380c31e0a6d8b86689adcb695b8d1ddf53714310976c520a51433887c8596c64
   - SHA256:f98960dc39dcf26f9825ea957244139e72bc71bf64f5a7c4a5f714ec9c53b252
   - SHA1:a8eff6f5dcf5e2dcc6c1eefffc99951543612c2a [weak]
   - MD5Sum:81ae2c24b7cc23144890c2db0cb64df5 [weak]
  Release file created at: Mon, 19 Oct 2020 10:07:06 +0000
Get:16 https://minio.k-space.ee/armbian/apt focal/focal-desktop armhf Packages [15.2 kB]
Ign:16 https://minio.k-space.ee/armbian/apt focal/focal-desktop armhf Packages  
Get:15 https://mirrors.netix.net/armbian/apt focal/focal-utils armhf Packages [4,858 B]
Get:15 https://mirrors.netix.net/armbian/apt focal/focal-utils armhf Packages [4,858 B]
Err:15 https://mirrors.netix.net/armbian/apt focal/focal-utils armhf Packages                                          
  
Fetched 2,387 kB in 6s (381 kB/s)                                                                                      
Reading package lists... Done
E: Failed to fetch https://uk.mirrors.fossho.st/armbian/apt/dists/focal/main/binary-armhf/Packages.gz  File has unexpected size (516030 != 453208). Mirror sync in progress? [IP: 82.145.63.161 443]
   Hashes of expected file:
    - Filesize:453208 [weak]
    - SHA512:2106846c18399ffc28b2da849488e65c512fdc5024e395233874da288a0f8bcd380c31e0a6d8b86689adcb695b8d1ddf53714310976c520a51433887c8596c64
    - SHA256:f98960dc39dcf26f9825ea957244139e72bc71bf64f5a7c4a5f714ec9c53b252
    - SHA1:a8eff6f5dcf5e2dcc6c1eefffc99951543612c2a [weak]
    - MD5Sum:81ae2c24b7cc23144890c2db0cb64df5 [weak]
   Release file created at: Mon, 19 Oct 2020 10:07:06 +0000
E: Failed to fetch https://mirrors.netix.net/armbian/apt/dists/focal/focal-utils/binary-armhf/Packages.bz2  
E: Some index files failed to download. They have been ignored, or old ones used instead.

 

Seeing this on XU4 and C1 as well.

Answering my own question here. apt upgrade resolves this issue.

After some time this is sorted out but issue is not solved. We don't synching mirrors properly and someone would need to check what is the proper way Probably a small problem, but so far we couldn't find that moment.

Yes, it was worth mentioning since it's the first tie I saw this. It is self correcting after apt upgrade.