Selective replication

Selective replication: ever had any problems with formulas being too long? Example :
SELECT FieldName="A":"B":"C":"D" |@AllDescendants
Sometimes it will replicate without taking notice of the formula (all documents) - sometimes it won't replicate !
Tip : shorten the formula/split the database.

Selective replication : not all documents are replicating.
The fieldname's value (used in the replication formula) has been modified by a user & the document will not replicate.
Tip : via script, remove the item & re-create it & that gets replication working.

Clearing history, ... we're all done.
If anybody else has come across this, I am interested in any info.