Well this post has gone off topic quite a bit.

My RadCity 5 Plus StepThru still has a low speed wobble that can initiate a whole-bike shimmy. It is not headset looseness, fork softness, spoke tightness, tire pressure or tire bead location. It has been to 2 bikeshops and 2 bike mechanics. All agree it is a combination of front for bridge and headset angle : in other words it is baked into the very geometry of the bike itself. My partner and I have each fallen off it twice in traffic and will no longer ride it. This is a dangerous bike.

So. It's been to the bike shop and was disassembled and rebuilt. There is however no change to the slow speed wobble although it is worse when there is the front rack and child seat installed. The bike shop are on 100% sure this is an issue regarding the bikes construction and geometry. Is ever so slightly rubbish.

Hi all, I've just taken delivery of my radcity 5 plus step through. At slow speed I definitely have a shimmy through the entire bike. The headset and stem are tight as is the front axle. Tyre pressures front and rear about 60. I have a front rack and a yep child seat on the rack. If I hold the front wheel between my knees and slightly shake the bars while facing the bike I do get a resonant wobble through the entire bike. Likewise at low speeds below 5 mph I get a wobble which means slow speed handling becomes very dangerous. I'm beginning to think that this is the bike geometry and construction at fault.