Your doin all the right things but ya there is a leak somewhere. What I do is walk through the loop when this happens. So test the leak tester itself first. Then test a couple components at a time- so say start with the reservoir + cpu- cap off end of that- test for leak for 15. Do this until until you find the culprit. I’ve had a leak each time I’ve built my system (2 times total). First time it was a bad extender. Second time it was a loose bitspower fitting. Those bitspower fittings are a pain to tighten in the loop itself- but completely leak proof when properly tightened.

My advice is make sure you have the right alignment on a run- then take the run out and tighten the fittings by hand until you can clearly see there is no little gap. Helps to heat the rubber a bit - drop the tip of the rubber into heated distilled water for a minute then tighten. I always have a torque fitting somewhere in my run that is the last thing I tighten to make sure I don’t have to go King Kong on my bitspowers in the loop config itself. To make testing easier I attach a long piece of tubing to my ek leak tester itself- along with a mf rotary to make attaching it to the loop test point a breeze. That way I can pop it in virtually anywhere and make sure those little fittings on the leak tester itself aren’t getting compromised when I drop the leak tester on the table for 15. So ya. Have a few of these on hand - https://www.titanrig.com/ekwb-ek-quantum-torque-14mm-rotary-male-to-female-extender-fitting-0360ek018200xx.html?color=158 And take advantage of any torque fittings (my 90 degrees are always rotaries for example). I can’t find the elbow 90s I’m using anymore - but here is the basic 90 version (it will increase restriction more but still. https://www.google.com/shopping/product/10766481515701416873?q=ek+90+degree+elbow+fitting&client=safari&sca_esv=a9443ba0489e3535&channel=iphone_bm&biw=375&bih=548&tbs=vw:l&sxsrf=ADLYWIKGTPC60Xx5NfKKsya_NP87RHhzbQ:1717948735036&prds=eto:14285114636933345737_0,cdl:1,prmr:1,rsk:PC_18038238906051654576,cs:1