In the turbulent times for Air Travel that we are in right now, I would recommend only use third party portals only when it’s absolutely necessary (use up the credit/company policy etc). Not even any of the multipliers are worth it.

Unless your travel agent / agency are on-point (-if you can literally call/text/e-Mail a specific person that you know will take care of you), you are opening yourself up for getting treated like a ball being kicking around.

If you do have to, and when you did book 3rd party, then you basically have to do what people do in the old days - call up/check online with the operating airlines to confirm your flight the night before. (Square away any schedule changes / ticket reissued if needed / your seat assignment are still there and not affected by an equipment swap etc etc. )