New JBL Crystalprofi e1901 constantly expelling air

[Rahms]

The vertical spray bar means the air builds up at the highest point, until eventually it gets pushed through as one, which is the gurgling. The air turning up in the first place is still your issue! Possibly the top joint on the spray bar which is out of the water.

Failing that, air being drawn in via the intake leg (potentially at a connection as well).

Always love a good filter mystery 😎