Ejecting but won't lock back on last round

[hound53]

Turns out I had a leak where the gas tube entered the gas block. Used some blue locktight on both it and the gasblock itself then torqued the gas block screws to 30 inch pounds. Fired 20 rounds today 10 each from both from a magazine and the BobSled. I had no feed issues with the magazine and it locked back after every round with the Bob Sled. I went down to 2.5 oz with the buffer weights, a bit heavy on the recoil but once I get the load development done I can play with the gas block setting or add weight to the buffer, the gas block was full open today

Update - went back on the 26th and the problem returned. Next step is replace the gas block and gas tube. At least now I know where the problem lies