Two stage filter system help

[nomand]

Hi, I have a fairly simple water system and I'm in the process of installing a two stage filtration system (instead of a single stage I had before).

Whole thing is just a Whale MK3 pump pulling water from the bladder, and pushing it through two filter housings and out the tap.

Filter 1 is a 1 micron sediment and Filter 2 is 0.5 taste odour & cycsts cartridges.



I'm having a couple of issues:

1. The foot lever has trouble returning after bottoming out and does so rather slowly. Either the spring is not strong enough to return it and needs servicing or the filters are way too fine for the pump? Maybe something else?

2. The actual water flow is good when pumped, but the water keeps flowing for quite some time after the mechanical pumping action has stopped. Is this the foot pump's fault? I would've thought once you stop pumping, the water flow stops also. I blew through the pump to see if it's in the "open" position when at rest and it was! I assume this is intended behavior, because the pumps manual suggests compatibility with an in-line electric pump that in this case would be pulling water through the pump without obstruction. But I would've thought the pump would close the flow! These are often used for salt water intakes and it's a horror show if it just sits open by design!
Anyway, this leads to another problem:

3. After little use, a siphon effect is created where the pump pressurizes the filter housings enough that the water flow keeps going, completely draining the housing of water (mine are transparent so I can see it happening). After which it's impossible to keep pumping water with the system full of air.

I've tried diagnosing if I have an air leak and I couldn't find any anywhere between the pump and the tap. I haven't looked at the pump itself though, except shining a light through the housing to make sure it's not full of air.

Maybe the pump is struggling to push through two filters and generates too much pressure that creates the siphon effect? Even though if that were the case, the pump shouldn't just let water through after pumping has stopped in my opinion.

Appreciate any pointers.
Cheers!