what manufacturer/type of 3,3 mF capacitor did you use (2 nA is really low: at which voltage?).
the first picture with the "artefact" in division 9+10 makes me think of some interference (perhaps with a switchmode supply).
I would put all into a metal cookies box.
The caps are Panasonic Series: M Typ: A 85°C 2000h.
Had two 3,3mF 25V for first test, one went down to ~2nA, the other to ~3,5nA @~11,5V.
They were formed @11,5V 48h + ~1week disconnected @20°C and <30%rH.
Perhaps my cheap SMPS with "high ripple" had an effect on that, for rechargeable batteries the positive effect with reflex/pulse charging is well known...
Tested with ADA4530-1 @12V as buffer for 12h with recording of voltage drop.
So the 2nA are before soldering, did not test after.
The scope was set with BW-limit to 20MHz (only option for this Rigol) and hires-mode turned on.
As it was a first test with bodged wires, I do not give a thougt on any residues or interference in the readings.
Sure it will go into metal cookie box with coax-cables and BNC-connectors and repeat the measurements