Small amounts of micro bubbles from return....

I've been having a big issue of small amounts of micro-bubbles coming from my return...it comes in spurts of about 10-15 second intervals...Water line is perfect in my sump...I get a small trickle of bubbles going into my fuge but it disappears once it comes back up...I have baffles up...my drain is going into a sock that helps with the bubbles...its not my skimmer, bubbles dont escape it, even if they do, it's not enough to affect the sump...even if i dial down the pump flow with a ball valve, it still has bubbles coming out of the locs. My return is opened all the way. I have a mag 9.5, with a coupling connected to a flex tube then a ball valve, flex tube again into a check valve, another flex tube that goes into the 3/4" bulk. i reglued all my return hoses last night and it still has small spurts of micro bubbles coming out into the DT. I cant seem to find the problem...it doesnt seem like i have any air coming into the return....IM LOST and GOING INSANE!!