Consulting the pros:

Does anyone have familiarity with the back-end of e-tickets on how OTAs manage control of a ticket?

For example, some OTAs, like O/XP/PL, it's very easy for airlines to reissue a ticket. You can often do this completely through their online platform. It seems O/XP/PL doesn't lock e-ticket control.

Other ones, particularly those OTAs charging agency handling fees, you can't be able to do so. This is probably intentional since they want to collect the fees and not have you go through the airline directly, unless travel has begun, or IRROPS from WX/MX/etc.

Does anyone know how various OTAs fall under in this regard: I'm looking at OTAs like Flighthub/Justfly, Vayama, travel2be, Cheapoair, etc.