This oil level is too weird... help !

[Externet]

Hi all.
Unpacked my dormant for a year compressor, and the oil level showed at the center 'full' sight glass line as should. Ran it for a minute to confirm if was still alive. Later noticed no oil at the sight glass. Tilted it and barely showed oil under the 'add oil' line.

Instead of adding oil, decided to place a rag under to capture any spill and removed the oil deposit pan straight down and oil started heavily dripping from the compressor guts to the reservoir to the point of showing a bit more oil than the 'full' line.
Am perplexed. Anyone has an explanation ?

A couple of times tried to learn from others with no success ---> Trying my luck again... Cornelius compressor 130R ~2103... Are you using one ?

----> Question for anyone actively using a Cornelius compressor, please.

----> Oil level in Cornelius, please ?

 

[Externet]

There is a fine screen between the crankshaft housing and the oil returning to the pan. Everything is super clean.
If the oil is too thick, or there is some vacuum above it, or if there is no venting under it; that should prevent the oil from draining downward showing no oil at the sight during and after operation, right ?

Pictured from under :

And another screen + filter in the pan for the oil pump inlet: