Terrible lag and occasional error 90006

Been experiencing really bad lags between 5pm - 12am (GMT+10) specifically. Other times seem to be perfectly fine. When the lag starts, these are pretty much the symptoms:
- people are generally teleporting around the map
- dualcasts are not being consumed
- once raise has been accepted, it takes 15-20s for my character to load
- when i use skills like benediction, it takes 15-20s for the skill to take effect
- spikes such as irregular loading castbar making raids mechs almost impossible to resolve
- interacting with retainers/chocobos take about 15-20s to load as well
- sometimes if the lag gets too much, i get booted out with an error 90006
- etc (I could load more symptoms but I think this is plenty enough)

I'm on PS4 connected to WiFi (Optus - NBN). I've had to swap to 4G the last couple of nights for raid, but it's not perfect, I still lag (just not as badly).

And before anyone mention it's an ISP issue, I've called up Optus and they've done a speed test and checked my NBN status. Both are normal. Things are loading perfectly fine on my other devices, and other games (i.e. Genshin) is perfectly fine too. This problem seems to only occur on FFXIV.

This only started happening 3-4 days ago, previously it was never this bad.

same issue here, been going on for a week, i need a solution