Hi, First, I noticed that some of the latest low profile M5 hex head bolts' socket, which I got in my CNC MINI Mill build kit are not as (consistently) deep as previous ones I have purchased from OpenBuilds. Some (Not All) were more shallow by some .2 MMs Second, The C-Beam end blocks 5MM low profile bolt hole reliefs are not always as large a diameter as the 5MM low profile bolt heads. Together these two things did cause an issue with one screw on my build. But it was my fault for trying to make the one of the M5 bolt's head flush as the others were. Maybe check your 5mm low profile bolt supplier?