A few possibilities.
I always give at least 30 seconds continuous agitation at start of dev process.
When agitating I find that moving the tank upwards and then flipping the tank over and letting the developer drop to the other end of the tank works best. If you just tip the tank over, especially if only done at moderate speed or slowly, causes dev to flow through sprocket holes and cause some of what I see in your negs. At the top of the up motion, the dev becomes weightless and is easily spun over with the tank without it flowing through sprocket holes.
Then tank is brought straight back down as dev falls down (not poured down).
Then repeat for how ever many times you want.
Also, you must rap tank on firm base straight after agitation as the reels can slide up the spool and out of the developer. Rapping the tank causes them to slide back down to bottom of tank. Obviously this may depend on your particular tank but it looks as if your reel mak have stopped in several different positions after each agitation cycle.