Since there isn't really a specific airbrush community, i'll try dumping my issue here ok? I'm following the Q/A structure of the airbrush subreddit for completeness sake :)

Alright, so I just got my first airbrush for my birthday - for mini painting - and I'm getting very unreliable / unpredictable paint flow after an initial clog and cleaning.

Airbrush make and model

Timbertech ABPST05

Compressor make and model

Same name, came with the set. Running just over 20 PSI during open airflow.

Paint or other medium you are using

First some Vallejo Black Primer with Vallejo AB Thinner, then some Scale75 White which clogged.
Now I'm struggling with Citadel Shyish Purple contrast paint with thinner despite its already very liquid nature.

Have you done anything different lately?

After thoroughly cleaning (stripping the whole thing, running Timbertech AB Cleaner through the pot -> nozzle etc) I slowly started noticing unreliable spray pattern:
I open airflow, then pull back ever so slightly -> a thin stream comes out for maybe a second -> stops. I pull back a little more -> a slightly bigger stream, then stops.
Once I hit a "wall" on the trigger, it starts working a little bit better but still not entirely reliable.
No bubbles appear in the tank during this.

Have you tried using just water, tear-down and cleaning...

Just water feels like it's working fine, just thinner also seems fine. I did a full tear down after it first clogged because that's how a YT video told me is the right way to clean an AB after every use T_T
I'm pretty confident that I put it all back together right.

I switched out needle, nozzle and cap. I let some cleaner flow through the pot, out the front without a nozzle on to check the channel isn't blocked.

Any advice would be appreciated!