That quarantine data unfortunately is encoded so Ignition is the only thing that can meaningfully deserialize it, and there is no easy way to get it into human readable format. Following the steps Paul outlines here may be your best bet to see what that data is.
Audit profile insert data and a few other operations (notably system.db.runSF functions) do not have their own exporters/importers yet for quarantined items, which is why you are seeing that data in base64 form. At this point, those are slated to be worked on in 8.2.
However, if the error is always that string or binary data would be truncated message, then that piece at least should be a relatively easy fix. You should just need to update the problem ‘string’ columns in your AUDIT_EVENTS table to use larger data types, something like varchar(1000) or varchar(MAX). For the future, to prevent this from happening with new tables, you would need to update your Translator settings for your MSSQL translator, and set the String Data Type Mapping to a similar varchar(MAX) value.