Hard to say without a better idea of the data model.
However, if you see $Syn tables, that could be a very good reason. As opposed to other RDBMS, and not being QlikView a RDBM itself, the way Qlik associates tables is when two tables share one or more fields with exactly the same name, case sensitive.
When two or more of those fields exist in two or more tables, a synthetic table is created. This, per se, is not an error and it may work just fine, as any other composite key, but in my experience, it often comes from errors in the data model.
Think of an "Order" table with an "ID" field, and think of a "Customer" table with an "ID" field. If there are no changes in the script, these two tables with be linked by the ID field, which may not be desirable (the Customer.ID has one format and the Order.ID has a different format, both refer to different entities, etc.).
Think now that both have an "Address" field, a synthetic table will be created for both tables, such synthetic table will include the cartesian product of the values of ID and Address.
The way the data model viewer represents this on screen is by another table with a "$Syn_" preceding the label of the table. This table does not really exist as such table (i.e.: you cannot refer to its contents in an isolated way), and oftentimes is referred to as "Syntehtic Key" instead.
https://help.qlik.com/en-US/qlikview/April2019/Subsystems/Client/Content/QV_QlikView/Scripting/synth...
In your case, $Syn4 means that 4 or more tables share at least 2 or more fields, I'd suggest to check whether this is how you want to load the data or rather, due to something similar to the example above, which could be solved by creating concatenated keys or removing redundant fields (for example, Customer.ID is only required twice, in the Order table and the Customer table, it may appear in the OrderLine table, which is redundant to the Order one).
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