why is my meta ads conversion tracking totally broken?

i am seriously at my wit's end with meta ads. the conversion tracking for my new saas is completely, utterly broken and it's driving me insane.

we just launched our app a few weeks ago, and i'm trying so hard to scale acquisition using meta ads, but the data is just totally unreliable. i can't trust anything i'm seeing in ads manager.

i've spent hours on this, literally hours. i've checked the meta pixel helper and it says everything is green, events are firing perfectly. i've looked at my standard events like purchase and lead, and even custom conversions, they all look configured correctly. i made sure my domain is verified in business manager and i've set up all the aggregated event measurement priorities, thinking that was the issue. i've even cross-referenced the meta data against our internal crm and google analytics, and there's a massive, gaping mismatch. i mean, it's not even close. i was so desperate i even deleted and reinstalled the entire facebook pixel setup from scratch, hoping for a miracle, but nope.

the problem is, meta ads manager reports drastically fewer conversions than what actually happens in our backend. we're talking like 50-70% less. it's insane. this makes our roas in meta look absolutely abysmal, totally impossible to trust any optimization decisions based on that. i literally have no idea which campaigns or ad sets are realy performing, it feels like i'm just throwing money into a black hole because i can't get reliable data.

what am i missing? seriously, what are the common, elusive reasons for such a massive conversion tracking discrepancy that someone new to this might completely overlook? i need to get reliable data asap, or i'm just burning cash for nothing.