Wind knots and line behind the spool, the problem lies elsewhere unless it is over filled. I would say you are a little under filled on that spool especially for float fishing , probably be ok on a feeder etc.
It's a tad underfilled, but not massively. Unlike a normal spool, those chamfered Shimano AR-C spools only need to be filled to just beyond the start of the chamfer. Fill much more and you can find line spilling off a little too easily. Line with a bit too much memory makes the issue worse.
If it's Maxima as it appears, i've found for 4-6lb the best way to spool it is to lay the spool flat rather than use a pencil and reel it on letting the line pass lightly through fingers to get rid of any twist.
Once loaded, when you go fishing attach a light 15-25g feeder and cast out as far as you can, maybe 40-50yds and reel back in fast, seems the combo of wet line and the weight of the feeder makes the line bed and lay lovely and i've never had an issue with line spilling off, wind knotting or line behind spool and i do tend to overfill my spools very slightly.
A little under I would say also. Tend to find that and especially if the line is new, that what you describe comes about when casting to different distances during a session, casting further tends to become difficult so the cast gets forced more, then once the line has come off and back on a few times, a short cast sees more line come off than was needed for the distance. In all cases, dab the spool just as the rig hits the water. You could and after spooling right up to the lip, find somewhere with some distance to settle the line down with a few casts.
I fill my Shimano spools up to just over the start of the chamfered part going up no more and don't have many problems. a lot of problems with line twist I found to be playing fish off the drag or free spool I reduce how much I do this now by back winding and have very few twists