You will have to resync these affected nodes from scratch.
Looks like they got stuck!
Newer bitcoin core have 2 useful
commands:
invalidateblock and
reconsiderblock to avoid long process of resync. I hope to see them on in zettel wallet too

Also making weekly backup of
blocks and
chainstate folders can help to return on right chain quicker.
And BTW, thanks for keeping the awesome blockexplorer alive.
But can you take a look at this bug here:

The total percentage seems to be wrong, in the case I show in the picture it should show 57.13.
Please fix this, thanks in advance.