SharedIds with duplicated languages

[LaszloKecskes]

During implementing the migration #4115 it was discovered that some instances have sharedIds, where one language has more than one entity (for example, a sharedId has entities for english, french, french). The following steps are needed to be taken:

• further examine the data (whether there are multiples with more than double, how consistent are the multiples wit each other)
• discover the cause of the multiplication
• fix
• migration to repair affected data

[LaszloKecskes]

Might be connected to #4149.