Have you inspected your cartridges for rips, tears, other damage?
The one on the left looks like it might have a tear in the blue rubber seat, at about 1:00 O'clock, right as the video starts.
If you find nothing wrong with the cartridges, check the manifold assembly at the top & the cartridge support at the bottom. Make sure they seat properly.
Are these new cartridges, or old ones that were around before the problem started?
How's your return flow, does it seem normal?
Your cleaning "only the air breather tube screen" and the pressure goes back to normal? Right?
Are you bleeding your filter /w the bleed valve up top, when you 1st fire it up after re-assy?
It seems like the filters are being bypassed to a degree at least, such that the breather tube is picking up junk, unfiltered out the return.
But yeah, that tiny little guy shouldn't cause it to stop functioning. All it is, basically, is an automatic air bleeder at the manifold. It pulls in unfiltered water and air, then sends it out the return. Hence the screen.
If there's that much junk, collecting that fast on the screen, then that means the filter isn't doing its job. Or the pool is ultra dirty, thus lots of junk filled water is making its way into that screen, since it's "pre filter".
