It’s a glitch found ages ago but IIRC thankfully quite tough to do (and I’ve never seen it live). It involves squad mates, one medic and one support I think. The support needs to limpet themselves in a particular spot and rag doll in such a way as they can be revived but are in an otherwise unreachable spot etc. The medic then redeploys with them.
I remember a map from Star Wars Battlefront 2015 where you could jump pack on top of a hanger. Nobody knew about it, and they were totally caught off guard when we shot at them.
The other “glitch” spot would be on the castle roofs on ballroom blitz. But that was kind of intentional because you could parachute onto it. That spot was op with snipers and support MG’s.