It looks like you're working with our Support team on this, which is great since they can look into your specific configuration and assist. If there are any insights that come from that process that could be beneficial to others in the Community, we appreciate you sharing here when it's resolved. Thanks!
I recommend contacting customer support for help. Support will likely do the following steps, and you can do the same if you are familiar with these things.
Check the audit log for the flow to see if anything changed.
Check the mapping on the NetSuite import to make sure the missing fields are being mapped correctly.
Check NetSuite to make sure the missing fields are settable in the UI on the same form and NetSuite role that the flow is using.
Enable debug logs for the NetSuite connection, and then run the flow again, and then check to see if values for the missing fields are being sent to NetSuite.
If the missing fields use a lookup to find a value, then perhaps the settings on the lookup are not accurate, or perhaps duplicates made it into NetSuite somehow, and now integrator.io cannot find a unique match, etc...
Maybe there is something in NetSuite that has changed like the role or form permissions being used by the flow, or perhaps some other setting in NetSuite was changed affecting this.
Regarding #3 and #4, very interesting, and you should consider opening a NetSuite support ticket in parallel and let NetSuite know you are using a SuiteScript to set this field using an Admin role and it is not sticking.